Notes: Rising from the ashes of the German-US MBT-70 program, the M-1 Abrams was designed to cure a major problem in the US arsenal – US (and most NATO) main battle tanks of the 1950s, 1960s, and 1970s were simply not able to match their Soviet counterparts, even with the many faults of Soviet armor at the time. Israeli experiences in the 1956, 1967, and 1973 wars simply confirmed those conclusions, as the Israelis were using many of the same tanks in those wars which would have to fight in Europe if World War 3 broke out. There was a growing realization that NATO had been very lucky that the Soviets had been too worried about Mutual Assured Destruction and what the Soviet leaders believed that NATO was capable of to actually start World War 3.

After the MBT-70 program (and a less-expensive and complicated alternative, the XM-803) went down in flames, US designers started from scratch. The Pentagon first appointed a special task force, comprised to a large extent of senior NCOs and officers with primary backgrounds as tankers; this task force, the MBTTF (Main Battle Tank Task Force) began their work in early 1972, and reported directly to General Creighton Abrams (then the Army Chief of Staff; as General Abrams died before the M-1 was fielded, it was given the name Abrams in his honor). It was quickly decided to use the new British armor known as Chobham (actually known by the code designation of "Burlington" in Britain – Chobham is a village near the labs where the armor was developed) for critical areas – but to the dismay of the British designers, the US Army’s Ballistic Research Laboratories actually improved upon Chobham. (The American version was unofficially called BRL 1, but it and later versions are simply referred to as "special armor" by the US military.) Several contractors submitted designs for the XM-1, but only the designs submitted GM and Chrysler survived to the prototype phase; in the end, Chrysler’s design became the M-1 Abrams. (Due to financial problems, Chrysler sold its Defense Division to General Dynamics in mid-1982; virtually the entire M-1 series has actually been built by General Dynamics Land Systems.) LRIP (Low-Rate Initial Production) began in early 1980, and full production in late 1981. First issue to Army units began in 1982, with the M-1 Abrams I.

Interesting Note: The first XM-1 was rolled-out on 28 Feb 80, with General Abrams’s wife and his 3 sons in attendance. It was not revealed until this ceremony that the name of the M-1 would be the Abrams. Up until just before the rollout of the XM-1, the tank was going to be called the Marshall (after the father of the post-World War 2 reconstruction plan, General George C MarshallI). However, it was felt that it was better to name the M-1 after Creighton Abrams, an armor hero that had fought since the end of World War 2 for the kind of tank that became the M-1, and rode herd over the initial M-1 design program; he had died of cancer in 1974, while still on active duty. When that first XM-1 was rolled out, the name Thunderbolt had been stenciled on the turret – this was the nickname Creighton Abrams usually gave to whatever tank had been assigned to him, throughout his career.

The M-1 Abrams I was the first version of the M-1 Abrams series, produced from 1980 to 1985. The M-1 was a quantum leap forward in tank design at the time of its introduction, with a comprehensive fire control suite, gun stabilization mechanism, and night vision devices. The use of the powerful AGT-1500 gas turbine engine was perhaps the first use of a gas turbine in an armored vehicle in a large scale – the gas turbine, being essentially a type of jet engine, offers incredible power, torque, and acceleration while remaining a relatively small (if fuel-hungry) unit. The AGT-1500 is also a multi-fuel engine, capable of burning gasoline, diesel, an ethanol/gasoline or diesel mix of up to 20%, JP-4 or JP-8 jet fuel, or kerosene; in extremis, the AGT-1500 can also burn pure ethanol or methanol with some modification. The M-1 also uses a special type of ammunition storage that was also rare up to that point: it incorporates blowout panels that use covers on top of the bustle which offer a "route of least resistance" in the case of an ammunition hit that causes the ammunition to detonate inside the vehicle. If the main gun ammunition supply in the turret (but not the hull) is detonated by a weapon hit, the M-1 is not automatically destroyed. Instead (in game terms), the main gun ammunition in the turret is destroyed, the armament, sensors, and electronics each take minor damage, and each member of the crew except the driver takes 50 points of concussion damage. 80% of the main gun ammunition carried on board the M-1 is carried in the turret. 2,374 M-1s were built before production shifted to the IPM-1. Most were later upgraded to the IPM-1 standard or to the standard of later models, but some were converted into M-104 Wolverine bridgelayers or mine-clearing vehicles. Those that do remain in service are found only in National Guard and Reserve units, and they are by 2008 found in very small numbers.

The primary armament of the base M-1 series is a modified version of the Royal Ordnance L-7 105mm rifled gun, designated the M-68 (the M-68 is slightly modified to allow the L-7 to use standard US gun mantlets). During the design process, the main armament was a bone of contention, primarily between the bean counters that wanted to save money and the military, who knew that the 105mm gun was rapidly becoming less and less capable of handling the newer Soviet tanks being fielded at the time. A compromise was eventually worked out – the M-1 would be armed with the L-7, but the turret was designed to that a variant of the Rheinmetall 120mm gun could be later retrofitted.

Like many armored vehicles designed to use diesel fuel, the entire M-1 series (except for some of the M-1A2 SEP tanks) had the ability to quickly lay a thick, oily smoke screen by spraying diesel fuel directly into the tank’s exhaust. The VEESS (Vehicle Engine Exhaust Smoke System) was no longer usable by the end of the 1990s, when most of the US ground vehicle fleet had been switched over to JP-8 as a motor fuel (it could still be sprayed into the exhaust, but as JP-8 doesn’t generate smoke in that manner, it was pointless). The VEESS was therefore removed. The M-1 series is also equipped with smoke grenade launchers (also common on modern armored vehicles). The original launcher was the M-250 system, which used twin banks of six smoke grenade launchers on both sides of the turret (using non-explosive 66mm grenades with red phosphorus filler and a launching charge to generate the smoke). The grenades are fired from inside the turret in groups of three; if necessary, up to the entire complement of 24 grenades can be fired at once. In 2004, replacement of the M-250 system by the new M-6 system began, though as of the time of this writing (May 08), not all Abrams tanks have had their M-250s replaced. The M-6 system is similar in appearance to the M-250, but more flexible; it is able to colored smoke, IR-defeating smoke, and flares (normally used to decoy the heat-seeking guidance systems that most fire-and-forget ATGMs use). (It should be noted that USMC M-1A1s use similar smoke grenade launchers [and later decoy/grenade launchers], but their launchers use twin banks of eight launchers on either side of the turret instead of six.) The M-1 has full NBC protection, including overpressure.

Production of the IPM-1 (Improved Product M-1, though sometimes, incorrectly, called the Improved Protection M-1) began in 1984, and by February 1985, it had replaced the base M-1 in production. The IPM-1 Abrams I’s primary improvement is the addition of a layer of depleted uranium mesh to the frontal arc of the turret and glacis (though initially viewed with suspicion by its crews, the greater protection was very much appreciated by those crews that went to combat with it). The IPM-1 also added a feature that had been requested by M-1 crews from the beginning – a bustle rack to carry most of their personal gear; on the M-1, the crew has to strap their rucksacks, duffel bags, sleeping bags, water cans, etc., to the outside of the vehicle, or fabricate ad hoc stowage racks of their own – or worse yet, try to put it in the already-cramped interior of the vehicle. The IPM-1 is unfortunately a little heavier, but for the most part performs the same as the M-1 above for game purposes. 894 of these vehicles were produced between 1984 and 1986; as with the base M-1, most have been upgraded to the standards of later models or converted into other M-1-based vehicles. Those IPM-1s that remain are found only in National Guard and Reserve units, in very small numbers.

In 1985, Abrams production switched to the M-1A1 Abrams II. The M-1A1 has further upgraded armor, and the main gun is replaced with an M-256 120mm gun; the M-256 is based on the German-designed Rheinmetall 120mm gun, but has fewer operating parts. The simplified gun weighs less than the Rheinmetall design and is less prone to mechanical failure, but has few parts in common with the German-designed gun. The M-1A1 has an integrated NBC overpressure system; in a chemical or radiological environment, the crew is not required to wear protective masks or clothing, as the air is filtered and cleaned before being pumped in from outside. The M-1A1 has air conditioning and heating. The US Army and Marines, as well as the Egyptian Army (which has production facilities in Egypt) use the M-1A1. In 2007, deliveries of 59 M-1A1 tanks began to Australia. The export versions are detailed below.

In 1988, M-1A1 production was further modified to a standard first called the M-1A1E1 during testing, and now referred to as the M-1A1HA (Heavy Armor). The M-1A1HA has a layer of depleted uranium mesh incorporated into the frontal armor of the turret. In 1991, new M-1A1s coming off the production line were built to the M-1A1HA+ standard, with a layer of depleted uranium mesh added to the glacis as well as the turret front. Most of them were originally deployed to Europe, and due to this, the M-1A1HA and HA+ modifications were often referred to as the "European Package." In addition, M-1A1HA+ tanks were equipped with an improvement to the fire control system.

In 1990, some 80 design and engineering changes were also added to the M-1A1. Many of these changes consisted of items like modified wiring, improvements for maintenance, and suchlike, but most were originally a result of requests for modifications from the US Marines. Rather than make a special version of the M-1A1 for the US Marines, the Pentagon directed that the modifications be made to all M-1A1s in production from that point forward, and the resulting package of modifications are often referred to as the Common Tank Changes, and the resulting tanks are sometimes called M-1A1 Common Tanks. Some more easily-noticed modifications include several more tie-down points, provisions for mounting a Deep-Water Fording Kit, and a mounting point for a position reference system. Though this modification of the M-1A1 still uses a common sight for the commander and gunner, space was made in the turret for possible future mounting of a CITV. (In 1994 and 1995, 134 additional M-1A1s were also transferred in ownership from the Army to the Marines, but it is notable that 84 of these did not have the Common Tank Changes, and as of 2005 still did not have them. I am unsure of their status today.)

After receiving their M-1A1s, the Marines further modified them by adding a Driver’s Vision Enhancement (DVE) system. This replaces the driver’s passive IR night vision system with a thermal imager, and (again, as of 2005), the DVE had still not been added to Army M-1A1s. In 2003, the Marines also began a further upgrade program. These modifications are primarily concerned with battlefield survivability, adding a newer version of the HA+ armor improvements, exhaust modifications to reduce the tank’s IR signature, and as-yet-undisclosed modifications that reduce the radar signature of the M-1A1 a bit. In addition, the thermal imaging systems for the commander and gunner were upgraded to 2^nd generation standards, improvements to target acquisition systems were made, and an eye-safe laser rangefinder with greater range and precision replaced the older laser rangefinder.

In 1999, the US Army began another M-1A1 upgrade program. This upgrade never had any official designation, but was unofficially called the M-1A1 Digitized, or simply the M-1A1(D). Though the US Army originally wanted this upgrade to be applied to all its M-1A1s, (bringing them partially up to M-1A2 standards) budget concerns prevented this, and only about 200 of these modifications were carried out (mostly to M-1A1HA and M-1A1HA+ tanks). The M-1A1(D) upgrade showed almost no external differences, but internally, several important features were added, providing a digital command-and-control system to the commander. The M-1A1(D) was given a compact computer, a keyboard and a small monitor at the commander’s station in the turret, an integral GPS system, radios upgraded to improve digital transmission bandwidth, and a wireless internet system. The computer’s software ties all these added elements together, and allows an M-1A1 with these modifications to communicate with other M-1A1s so equipped (or, for that matter, other vehicles or sites so equipped). Continuous battle updates are therefore possible, along with the transmission or receipt of updated tactical plans, maps and map overlays, operations orders, and other vital information. Though it is unconfirmed, it is rumored that computers in an M-1A1(D) and later such computer-equipped Abrams tanks also have USB and Firewire ports as well as slots for flash memory and SD memory cards.

A note on the mounting of the external machineguns of the M-1 and M-1A1 series is in order here. On Abrams tanks, the version of the M-2HB used as a commander’s machinegun is technically designated the M-48. There are a few differences in the actual machinegun between the M-2HB and the M-48; the M-48’s charging handle is on the left side of the weapon, and consists of a stirrup-like handle connected by a chain to a rod that looks like a longer version of a standard M-2HB charging handle. Feed is from the right side of the receiver and case/link ejection is to the left; a bag or box can be attached to the left side of the M-48 to keep the spent brass and links from rolling and bouncing around on the turret or into the commander’s hatch. On the M-1 and M-1A1 series tanks, the commander’s machinegun is mounted on a CWS (Commander’s Weapon Station, or "Chrysler Mount,"), which is a low cupola with power controls for rotating the turret and vision blocks. The M-48 is attached to a mount that allows the machinegun to be trained, aimed, and fired while the commander’s hatch is closed, and includes a 3x periscope to assist in aiming. The M-48 can also be unlocked and used in the same manner as a pintle-mounted machinegun. (It should be noted that when the commander uses the M-48 while buttoned up, the loader’s machinegun and the antennas at the rear of the turret can get in the way of the traverse of the CWS; if the loader’s hatch is open, that gets in the way of the CWS’s traverse as well.) Notably absent is a way to reload the M-48 while buttoned up. The other external machinegun, an M-240 GPMG (usually a standard infantry model, but an M-240 modified with spade-grips can also be mounted), is mounted at the loader’s hatch on a simple skate-type pintle mount that runs from the left side of the loaders hatch to the right front of the hatch. The loader’s machinegun tends to obscure the commander’s vision through his vision blocks when the tank is buttoned up, and many M-1 and M-1A1 crews in Iraq have found that in urban combat, it is often better to remove the loader’s machinegun before entering such an area.

A minor variant of the M-1A1, the M-1A1KVT (Krasnovian Variant Tank) is employed by the OPFOR at the National Training Center at Ft. Irwin; these are older, generally little-upgraded versions of the M-1A1 that have been turned into VISMODs of the newer generation of Russian-made tanks with the addition of sheet metal, fiberglass, plastic additions to alter their external shape. They remain combat-capable vehicles, and their modifications can be easily removed if combat service is necessary.

In 1994, the US Army suspended the refurbishment of their M-1A1s going through depot-level maintenance, opting instead for a rebuild program called AIM XXI (Abrams Integrated Management for the 21^st Century). This has now become the standard for M-1A1 tanks still in US Army and Marine service, as well the base standard level for M-1A1s that are exported to other countries. (A few of these iterations of the M-1A1 are still in US service at the time of this writing in May 2008, primarily with the US Marines.) The AIM XXI program essentially rebuilds the M-1A1 from the ground up, refurbishing all systems to nearly-new condition, and (if the M-1A1 in question does not already have them), upgrading the armor to HA+ standards, adds the Common Tank modifications, adds the eye-protective vision blocks to the commander’s station that the M-1A2 uses, and (if export restrictions allow it), adds improvements to the fire control and target acquisition systems, upgrades the thermal imager to 2^nd-generation standards, and includes the M-1A1(D) upgrades.

The M-1A2 Abrams III version of the Abrams began production in 1992, with deliveries beginning in November of that year. The accent on the M-1A2 was survivability, but it also tied together many of the disparate upgrades that were done to previous models. The M-1A2 was originally to have a greater level of armor protection than even the M-1A1HA+, but the GDLS designers quickly discovered that this would have increased the weight of the already-heavy M-1A2 design by another 4 tons, and protection remained at M-1A1HA+ levels. Nonetheless, a redesign of the armor allowed GDLS to keep the same level of protection as the M-1A1HA+, yet lighten the armor package. The redesign also made armor damage easier to repair.

The ammunition racks in the turret bustle were also redesigned and rearranged, allowing them to hold an additional two rounds of main gun ammunition. Perhaps the most noticeable external difference from the M-1A1 series is large, drum-like periscope ahead of the loader’s hatch; this is the CITV (Commander’s Independent Thermal Viewer). Though there had been space in the M-1A1’s turret for a CITV since the M-1A1 Common Tank modifications, the CITV was not installed until the advent of the M-1A2. The CITV was an important addition, and one that Abrams crews had been clamoring for from almost the beginning. Until the M-1A2, the sighting and thermal imaging system on an Abrams was shared by the gunner and commander; since the gunner had priority on the sights when engaging targets, the commander had to look for new targets by standing up in his hatch and viewing the battlefield through binoculars or a hand-held image intensifier or night-vision device of some sort. The CITV allows the commander to look for new targets as the gunner is engaging other targets – making the M-1A2 crew into "hunter-killers" and increasing by as much as 50% the rate at which the M-1A2 crew can find, engage, and destroy targets. If necessary, the commander can also access the gunner’s sight and viewer, and overrides for the main gun and coaxial (long a part of tanks in the world, including earlier versions of the Abrams) allow the commander to quickly attack close-range targets that the gunner may not have time to notice in the heat of battle.

Another very noticeable difference between the M-1A1 and the M-1A2 is found on the left side of the bustle rack – an APU. It had long been known that fuel consumption of the turbine engine of the Abrams is almost as high when the tank is idling as it is when moving at full speed; when the Abrams has to idle in place for long periods (such as when conducting overwatch duties, waiting in ambush, defending a fixed position, etc.), an Abrams can burn through entire tanks full of the same fuel it needs to move. (During Desert Storm, a lot of M-1s ran their fuel tanks dry just idling, before fuel trucks arrived.) Makeshift solutions, such as BRAs (Battlefield Refueling Apparatus – 303-liter rubber fuel bladders with portable pumps) strapped to the sides of the hull and/or turret, proved to be ineffective and downright dangerous – most crews would immediately drop them the first time they were fired upon, and during the initial invasion of Iraq in 2003, one Marine M-1A1 burned up after one of its BRAs was penetrated by API small arms fire (the crew got out safely). An add-on APU was available in limited numbers for the M-1A1 – but mounted on a semi-makeshift rack that sort of hung off the left rear deck, and having only thin steel plating to protect it, it was vulnerable to enemy fire and everyday damage as well as being just plain clumsy. The M-1A2 adds a diesel-powered APU of conventional design in order to cut down on this extra fuel use, mounted in an armored box and taking up almost the entire space where the left side of the bustle rack was.

The M-1A2 not only has the same sort of digital command-and-control package as the M-1A1(D) – it improves upon it. The entire system is tied together with a more powerful computer and a set of sub-processors to control various elements of the system. An IFF (Identification Friend-or-Foe) unit was added, allowing the M-1A2 to broadcast a signal to friendly units to help keep it from becoming a victim of "friendly" fire. Like modern cars, small microprocessors also control aspects of the M-1A2’s mechanical operation, as well as providing diagnostic information for the various subsystems of the tank – leading to one of the nicknames for the M-1A2, the "Electric Tank." The M-1A2’s systems also make part of the FBCB2 integrated battlefield system; the crews of vehicles with IVIS (Inter-Vehicular Information System) can keep in secure real-time contact at all times, which gives them an important edge in today’s rapidly-changing battle situations.

Other external differences in the M-1A2 include the vision blocks around the commander’s hatch; they give a wider field of vision, and are designed to protect the commander from laser dazzlers (lasers designed to blind enemy troops) and other types of lasers that may not be eye-safe. The mounting of the commander’s M-48 machinegun is also different – the complex CWS is completely gone, replaced by a simple pintle mount and a ring of vision blocks mounted directly on the turret around the commander’s hatch. This reflects the prevailing attitude at the time of the M-1A2’s inception – the commander’s primary job is issuing orders, receiving instructions, and looking for new targets, and the M-48 is only supposed to be a backup "emergency" weapon for close combat. (This proved to be a bad decision in light of the type of combat occurring in Iraq and Afghanistan, as the crews often find themselves fighting buttoned up. Modified versions of the Stryker-type RWS’s are belatedly and very slowly being added to M-1A2-series tanks.)

The M-1A2 SEP (System Enhancement Package; its crews also refer to this version as the "SEP") further improves on the command-and-control system of the M-1A2, as well as increasing survivability and some improvements in other elements. The SEP began deployment in 2001, though the improvements that eventually became the SEP began design in 1994. Unlike most other members of the Abrams series, the M-1A2 SEP fleet consists almost completely of upgraded M-1, M-1A1, and M-1A2 tanks, some of which have been almost totally rebuilt. The SEP is now the standard version of the Abrams in production; most US Army Abrams are built to at least this level.

The computers of the SEP are enhanced, using faster processors and greater amounts of faster memory; disk storage was also increased. The interface for the computer OS is also simplified, making data input and general use of the system far easier; in addition, the small computer monitors used in the M-1A2 SEP are also color monitors instead of monochrome. The commander’s and gunner’s thermal imagers are replaced with a 2^nd-generation FLIRs – more akin to a FLIR one would find in a helicopter or aircraft than one would normally find in a ground vehicle. Fire control and target acquisition is also improved, making both faster. Additional armor, more advanced than used on the base M-1A2, was added to the SEP’s frontal arc; though the composition of this improved armor has not yet been revealed, it is widely believed that it is still based on the DU mesh of other Abrams models.

The APU of the M-1A2 was found to have many shortcomings; it had a large thermal signature, it was bulky, and vulnerable to enemy fire due to its comparatively thin armor (capable of stopping little more than heavy-caliber small arms rounds). In addition, the APU’s mounting resulted in a huge loss of storage space to the crews, meaning that the crews once again found themselves tying large amounts of gear to whatever space they could find on the exterior of the vehicle, which can cause lots of tactical headaches. The SEP does not have this APU, but in part of that space (less than half of it), the SEP does have small air conditioning unit called a TMS (Thermal Management System; according to the Army, the TMS is there to protect the electronics, not provide crew comfort.). The TMS does not provide heavy-duty cooling – it merely maintains the interior temperature of the tank at a level between 80-95 degrees Fahrenheit (and the metallic surfaces of the interior of the M-1A2 SEP can still rise as high as 120 degrees), even if the external temperature rises as high as 140 degrees Fahrenheit. The computers and other sensitive electronics also have additional cooling systems.

The loss of the bustle-mounted APU, however, merely brought back the problem of high fuel consumption. GDLS designed a gas turbine APU (called a UAAPU – Under-Armor Auxiliary Power Unit) that is so much smaller in size that it can fit under the SEP’s armor, on the right rear side in a space made possible by rearrangement of the SEP’s fuel tanks (and deletion of one of them). Budget shortfalls stopped this APU installation for nearly ten years, but in the interim, a possibly better solution was found – banks of advanced, compact batteries that fit in the same space that the gas turbine APU used. These batteries can provide power for the SEP’s systems for about 8 hours, a period in which even an APU-equipped SEP would burn about 600 liters of fuel. The SEPs also have a regulator system for the batteries, as a problem would often crop up with earlier Abrams tanks where the batteries would get ruined due to overcharging. The regulator system allows the batteries to be charged up only to their maximum capacity. Once the battery system was available, no SEPs were supposed to actually get the gas turbine APUs, and those that did had the APUs were supposed to have them replaced with the battery system instead. Unfortunately, budget problems have intervened, and the less-expensive UAAPU units have ended up equipping almost all of the SEP fleet. The cost of the APU (or the battery system) is fuel capacity – it’s taking the space normally occupied by one of the Abrams’ fuel tanks. The entire M-1 series have four fuel tanks, but the loss of the fourth fuel tank in the SEP costs the SEP 231 liters of fuel capacity.

Based on experience in Iraq (especially in urban warfare and close combat), the US Army has designed the TUSK (Tank Urban Survivability Kit). The origins of the TUSK were field modifications by individual Abrams crews and by their parent units (at various levels). Many of these modifications were standardized and improved, producing the TUSK. The TUSK can be added to any Abrams series tank (and some other vehicles), whether in part or using the entire kit. The modifications are designed to enhance survivability of the crew and tank, as well as help the M-1 operate more efficiently with attached infantry. The TUSK modifications give the M-1 lugs for ERA on the side skirts (which have proved quite vulnerable to RPG rocket penetration), louver-type spaced armor for the turret sides, slat-type armor for pre-detonating shaped charges on the rear of the tank, screens to prevent Molotov cocktail-type weapons from pouring into the engine, armored gun shields for the loader’s machinegun, and a remote weapons station for the commander’s machinegun so that he may aim, fire, and use his night vision for his machinegun while inside the protection of the tank. The RWS used on the commander’s station (a variant of the M-151 Protector CROWS used on the ICV version of the Stryker) also allows for the substitution of the M-48 variant of the M-2HB with a Mk 19 grenade machinegun, M-240B GPMG, M-249 SAW or standard M-2HB machinegun. The TUSK RWS (currently designated the XM-101 RWS) includes a daylight video camera, its own thermal imager, and a fire control system that includes a laser rangefinder, a small ballistic computer, and armament stabilization (providing the commander a total +3 rangefinder modification to hit rolls).

The loader’s machinegun mount is also modified with bracket for a "clip-on" thermal camera. At the rear of the vehicle is a field telephone-type device to allow infantrymen on the ground to communicate with the tank crew, while using the tank as cover (this was common on World War 2-era tanks, but hasn’t been so since). The modifications are designed to be able to be accomplished by second-echelon maintenance troops in the field, without the tank having to go back to a maintenance depot for modifications.

The US Army is also looking at the future deployment of a "hard-kill" APS (Active Protection System) for the Abrams and some other vehicles. This is a system similar to the Russian Arena or Drozd, or the Israeli Trophy and Iron Fist, using a buckshot-like burst of large-caliber balls or fragments, or a small missile that explodes near the incoming projectile to the same effect, to destroy incoming ATGMs and rockets. A set of sensors (short-range radar, laser-based, IR-based, or any/all of the above) detects these threats and automatically launches the countermeasure weapons, sometimes also launching smoke or flares to further confuse the incoming missiles and hide the protected vehicle. US deployment of a hard-kill APS (tentatively called "Quick Kill") has been the subject of much controversy – most of the Army brass originally wanted to simply buy the Israeli Trophy system and license-produce it; but they were overruled by Secretary of Defense (at the time) Donald Rumsfeld and some of the generals in charge of procurement of new systems for the Pentagon, since they favored a new system under development (and still under development) by Raytheon. Congressional hearings have been and are still being held, due to charges to charges of graft, corruption, and kickbacks (i.e., bribes) being paid to Rumsfeld and the generals involved by Raytheon). Raytheon’s hard-kill APS system is said to be far more complex, yet less effective, and has been plagued by repeated delays and cost overruns; current estimates have it going into service no earlier than 2012, and many military experts place it in service in 2016 or later. Meanwhile, there is a growing movement in the Pentagon and Congress to go ahead and adopt the Israeli Trophy system, either while Raytheon’s APS is under development or in place of it. As of May 2008, US vehicles are still not being protected by an APS.

That said, the US Army is doing experimentation and limited combat-testing of a "soft-kill" APS (using the sensors mentioned above and an array of countermeasures) is ongoing. Collectively known as the M-1A2 P31 modifications, the current experiments and test are based on M-1A2 and M-1A2 SEP tanks, and add automatically triggered laser dazzlers and countermeasures (called the VIDS system; in game terms, laser-guided missiles are one level more difficult to hit with, and those using laser rangefinders against the protected vehicle must make a Difficult: INT roll to get a proper range if the VIDS is operating). The laser can also be used (manually) to attempt to temporarily blind an enemy gunner (Difficult:INT; range 2000 meters). The VIDS also includes a laser sensor that triggers the VIDS system. An IR sensor is also included; this activates an IR jammer to decoy heat-seeking missiles (in game terms, most fire-and-forget ATGMs are one level harder to hit the protected vehicle with, unless the missile description states that it does not use IR guidance). The IR sensor can also trigger IR-obscuring smoke and flares if needed. An electro-optical jammer is used confuse missiles using MCLOS and SACLOS wire-guided missiles; at short ranges (about 500 meters), it can also confuse the actual guidance units of the ATGM launchers themselves as well as laser designators (as this is an automatic system, such jamming has a base roll of 14 to succeed). The P31 program also includes modifications to the Abrams to lower the IR signature and noise levels of the tank. The P31 modifications add launchers for 32 additional flares and 32 additional IR-obscuring smoke grenades.

There are a number of other modifications and improvements to the Abrams the US military is experimenting with or considering for future deployment, or possibly even waiting in the wings. One of these is the replacement of the gas turbine engine with a conventional multi-fuel engine. This is something that has been requested by potential export customers since the US began exporting the Abrams, as the gas turbine engine is expensive to build and maintain, and the high fuel consumption scares off a lot of potential customers (especially in the tight energy market of today). Because of the manufacturing cost, even the US military has not bought a new AGT-1500 engine since 1992, repairing, rebuilding, and refurbishing the existing ones instead. (Older Abrams tanks or power packs from severely damaged or worn Abrams tanks are also routinely stripped for parts, since even the manufacturing cost of the parts for the AGT-1500 is rather high.) Those engines are therefore, despite the best efforts of maintenance personnel at all levels, becoming more and more worn, and the wars in Iraq and Afghanistan have greatly accelerated this process. Many maintenance personnel believe that the existing engines will never be able to operate at peak efficiency again, regardless of complete any refurbishment attempt may be. Perhaps the most likely possible replacement for the AGT-1500 is the latest version of the Teledyne Continental AVDS 1970-2C, which is a conventional-type multi-fuel supercharged engine that also develops 1500 horsepower. Older versions power a number of military vehicles in the world, and these engines are therefore still in high-rate production (including license-production in several countries), spare parts are easy to find, and manufacturing and operating costs are much lower than the AGT-1500. Another often-mentioned replacement is the MTU EuroPowerPack, which uses an MTU 883V-12 diesel engine developing 1500 horsepower coupled to a Renk HSWL 295TM automatic transmission unit.

Another often-mentioned upgrade for the M-1A2 and M-1A2 SEP is a longer main gun barrel. Like small arms, a longer main gun barrel would allow the rounds fired from the gun to achieve a higher muzzle velocity, which translates into greater range. Several European countries are already developing or actually fielding longer gun barrels for their existing main battle tanks, and most of these upgrades are in the form of a replacement kit for the gun barrel. Fitting a longer barrel would therefore be a simple and relatively inexpensive upgrade. Many military experts, however, think that with recent combat experiences, taking place so often in urban and other built-up areas, a longer barrel would actually be a hindrance instead of a help (rotating the turret with a longer gun is more difficult in tight city environments), and a longer barrel is unnecessary in such short-range engagements anyway. The most commonly-mentioned upgraded barrel length is L/55 (the length of the barrel is 55 times the size of the bore of the gun – 120mm in the case of the M-1A2), in contrast to the current L/44 length of the M-256 gun currently used on the M-1A1 and M-1A2 series.

A have put a version of the M-1A2 SEP with diesel engine and an L/55 gun in the charts below. This version is (in some circles) being unofficially (and let me stress that, unofficially) being called the "M-1E3" or "M-1A2E1," sometimes along with the name "Abrams IV" being used. Since I need to call it something, and I don’t want to give the entry some ridiculously long name, I have used the term "M-1A2E1 Abrams III" below. This also avoids confusion with the fictional M-1A3 Abrams IV, which is found on the "Best Tanks that Never Were" page (and has become a Twilight 2000 staple vehicle for most players). And let me say it one more time – the designation is unofficial.

Export models of the M-1 series usually have some differences from the ones used by the US. Though M-1s of various models were tested in several countries who wanted to replace older tanks with state-of-the-art tanks, the first export customer for the Abrams was Egypt. The Egyptian M-1A1 contract was for base M-1A1s, without the later upgrades or the DU mesh armor improvements. The original size of the Egyptian M-1 fleet was to be 755 M-1A1s, but they recently have received permission (along with GDLS) to begin a modernization program for their M-1A1s – they will be modernized to full M-1A2 SEP standards (but see the note on their armor below), and in addition the Egyptians will also buy an additional 250 M-1A2 SEPs that have been rebuilt from M-1A1s, for a total M-1A2 SEP fleet of 1005. (The Egyptians have sort of a partial license for M-1 production – the Egyptians produce most of the hull, turret, and power pack components themselves, but they are closely overseen by GDLS personnel. In addition, the Egyptians are not permitted to produce or maintain the special armor components of their M-1s – these are made at GDLS’s Lima Army Tank Plant in Ohio, and damaged parts of the special armor sections are sent back to Ohio for repair and/or replacement.)

Saudi and Kuwaiti M-1A2s are for the most part the same as standard M-1A2s, but are equipped with air conditioning units as well as APUs, both of which are manufactured in Saudi Arabia. (The air conditioners are said to be much better than those on the M-1A2 SEP.) Their IVIS systems and computers are the same as those used in the M-1A2 SEP. Kuwaiti and Saudi M-1A2s are almost always seen with mine plows installed, though it is not a permanent installation and can be removed. The fire control system is to a lesser standard (what has been left out has not been revealed). Maintenance it carried out in Saudi Arabia, except for the special armor, and GDLS also monitors the maintenance carefully.

As far as the Egyptian, Kuwaiti, and Saudi M-1A2s go, there are a lot of conflicting rumors (even among reliable sources) that the M-1A2s used by those three countries do not have a DU mesh layer in their armor packages. I have not been able to find any definitive yes or no on the DU mesh for the Middle Eastern M-1A2, but I can think of a number of reasons why the US might not want Middle Eastern customers to have large amounts of depleted uranium available. (And I’ll leave it at that to [hopefully] tame the flame emails…). I have been able to find out that the US and most Western European arms manufacturers will not sell DU penetrators to most Middle Eastern countries, though the Saudis are apparently able to obtain them through "other means" (most likely Russia and former Soviet republics or the Chinese). In the charts below, I have some versions of the M-1A2 and M-1A2 SEP listed as "Egyptian (v2)" and "Saudi/Kuwaiti (v2)." Those entries account for the possibility that these countries may have versions of M-1A2 without DU mesh armor inserts.

The latest export customer for the M-1 is Australia. The Australians chose the M-1A1 to replace their aging AS-1 Leopards; their first M-1A1s arrived in Australia in September of 2006, and a total of 59 were bought and deliveries are now complete. (At the same time, Australia also bought a small fleet of support vehicles for their M-1A1s, consisting of M-88A2 Hercules ARVs from the US and the German MAN TGA HET [Heavy Equipment Transporter]. The MAN TGA HETs are to be license-produced in Australia.) The Australian version of the Abrams, designated the M-1A1 AIM SA (the "SA" standing for "Situational Awareness"), is essentially a "fully loaded" M-1A1 with all the refurbishments, modifications, and updates available to the M-1A1 under the AIM XXI rebuild program. In addition, the M-1A1 AIM SA is equipped with an inertial navigation system to supplement the GPS navigation system, and the updated FBCB2 system that equips the newest versions of the M-1A2 SEP. The M-1A1 AIM SA will burn diesel fuel instead of JP-8, though this required no modifications to the engine, and M-1A2 AIM SA tanks retain the multi-fuel capability. Except for the commander’s machinegun, the machineguns on the M-1A1 AIM SA are standard MAGs instead of the American M-240 versions.

Though early rumors suggested that the M-1A1 AIM SA did not use DU mesh inserts in its armor package, it is now believed that the Australian M-1A1s do in fact have the DU mesh inserts. (What the Australians did not buy were any rounds using DU penetrators – though since they have standard M-256 guns, their M-1A1s are quite capable of firing ammunition with DU penetrators.) The M-1A1 AIM SA’s were delivered in desert sand paint, though I have not been able to find out what finish they are now wearing. The Australian crews were trained for about two years at Camp Pendleton in California by the US Marines in the use of the M-1A1 – the Marines were reportedly quite impressed by the Australian crews’ proficiency even before training commenced, and even learned some interesting new combat tactics from the Australians. In addition, some of the Australian modifications to their M-1A1 tanks are being given a serious look for inclusion into USMC M-1A1s, after the Marines saw the additional capabilities of the M-1A1 AIM SA.

Most export Abrams are also equipped with radios that are used by the rest of the customers’ armed forces; in addition, the software, gauges, and controls display the language appropriate to the customer (there are unconfirmed rumors that even the Australian M-1A1s have software, gauges and labels that use Australian-dialect spellings of words and even Australian jargon!).

Twilight 2000 Notes: In the Twilight 2000 timeline, about one-quarter of the US Army’s M-1s at the time of the Twilight War were M-1A2s, and only about 5% were M-1A2 SEPs. The bulk of US Abrams were M-1A1s, but less than a quarter were of the M-1A1(D) type; most of these M-1A1(D)s were used as command tanks, and a very small number were used as scouts. A common addition to Twilight War M-1A1s in US units was a CITV. The AIM XXI program simply never got off the ground.

The Egyptian plant making the export version of the M-1A1 was put out of action early in the Twilight War – not by the Israelis, as you might think, but by the Libyans. The Egyptians ended up with only 202 M-1A1s before the destruction of their plant.

Some 112 M-1A1s were also sent to China in sort of a "Lend-Lease" program. These Chinese M-1A1s were equivalent to early-model M-1A1s (and in some cases, actually were early-production M-1A1s). Their Russian opponents at first thought the US had sent troops to China until they found out about the exported M-1A1s.

The Saudis only received 31 of the M-1A1 order, the Kuwaitis got a grand total of 3, in the Twilight 2000 timeline. The Australian M-1A2 AIM SA never existed in the Twilight 2000 timeline. None of the possible future improvements listed above were done in the Twilight 2000 timeline, and no sort of active protection system was ever considered. The TUSK never existed as a factory-manufactured kit, but the same sorts of modifications were carried out in part or whole on virtually any sort of military vehicle in the Twilight 2000 timeline.

Merc 2000 Notes: The M-1A2 was also sold to the Turks. Their M-1A2s have the full M-1A2 armor package and fire control system, but are equipped with M-1A2 SEP-type IVIS systems.

*The armored box in which the M-1A1’s add-on APU has an Armor Value of 2. Fuel consumption of the unit is 15 liters per hour, and it uses fuel from the M-1A1’s fuel tanks.

**The armored box of the M-1A2’s APU has an Armor Value of 3. Fuel Consumption of the unit is 11 liters per hour, and it uses fuel from the M-1A2’s fuel tanks.

***The UAAPU of the M-1A2 SEP is under the left rear hull, and has no armor value of its own. It consumes 9 liters per hour. The "battery APU" does not consume fuel, but adds $1500 to the cost of the M-1A2 SEP. (Incidentally, the armored box of the M-1A2 SEP’s TMS has an Armor Value of 5; the fuel use is included in the general fuel use of the M-1A2 SEP.)

****The bar armor attached to the M-1A2 and its variants as part of the TUSK kit functions against explosive rounds the same way as spaced armor in the Twilight 2000 v2.2 rules, but subtracts only 1D6+2 of damage instead of 2D6. It is not, however, true spaced armor, and will not help against AP and KE-type rounds; 2 points of armor on the HR are not counted against such rounds, and any benefits from spaced armor are also not counted against AP and KE-type rounds.