The M1 Abrams is a third-generation main battle tank produced in the United States. It is named after General Creighton Abrams, former Army Chief of Staff and Commander of US military forces in Vietnam from 1968 to 1972. The M1 is a well armed, heavily armored, and highly mobile tank designed for modern armored ground warfare.[6] Notable features of the tank include the use of a powerful gas turbine engine (fueled with JP8 jet fuel), the adoption of sophisticated composite armor, and separate ammunition storage in a blow-out compartment for crew safety. With a weight of close to 68 short tons (almost 62 metric tons), it is one of the heaviest main battle tanks currently in service.

The M1 Abrams entered U.S. service in 1980, replacing the 105 mm gun, full tracked M60 Patton.[7] It did, however, serve for over a decade alongside the improved M60A3, which had entered service in 1978. The M1 remains the principal main battle tank of the United States Army and Marine Corps, and the armies of Egypt, Kuwait, Saudi Arabia, Australia, and in 2010 Iraq. It is anticipated to continue in U.S. service until the 2050s, approximately 70 years after adoption.

Three main versions of the M1 Abrams have been deployed, the M1, M1A1, and M1A2, incorporating improved armament, protection and electronics. These improvements, as well as periodic upgrades to older tanks have allowed this long-serving vehicle to remain in front-line service. The M1A3 is currently under development.

Unlike earlier US military vehicles from World War II through Vietnam, which used a scheme of dark brownish green known as “olive drab” with large white stars, prototypes and early production M1 (105 mm gun) & M1-IP models used the flat medium green paint; and the large white insignia stars have transitioned to much smaller black markings. Some units painted their M1s with the older MERDC 4-color paint scheme but the turn-in requirements for these tanks required repainting them to solid green. Therefore, even though a large number of the base model M1s were camouflaged in the field, few or none exist today.

M1A1s (120 mm gun) came from the factory with the NATO 3 color camouflage Black/Med-Green/Dark-Brown CARC paint jobs. Today M1A1s are given the NATO three color paint job during rebuilds. M1s and M1A1s deployed to Desert Storm were hastily painted desert tan. Some, but not all, of these tanks were re-painted to their “authorized” paint scheme. M1A2s built for Middle Eastern countries were painted in desert tan.

Some M1 series tanks are being painted desert tan for service in Iraq and some are not. Replacement parts (roadwheels, armor skirt panels, drive sprockets, etc.) are painted overall green, which can sometimes lead to vehicles with a patchwork of green and desert tan parts.

Australian M1A1′s were desert tan when delivered but have undergone a transition to the Australian Army vehicle standard ‘Disruptive Pattern Camouflage’; a scheme that consist of black, olive drab and brown.

The Abrams is protected by armor based on the British-designed Chobham armor, a further development of the British ‘Burlington’ armor. Chobham is a composite armor formed by spacing multiple layers of various alloys of steel, ceramics, plastic composites, and kevlar, giving an estimated maximum (frontal turret) 1,320–1,620 millimetres (52–64 in) of RHAe versus HEAT (and other chemical energy rounds) and 940–960 mm (37–38 in) versus kinetic energy penetrators.[26] It may also be fitted with reactive armor over the track skirts if needed (as in the Urban Survival Kit) and slat armor over the rear of the tank and rear fuel cells to protect against ATGMs. Protection against spalling is provided by a Kevlar liner. Beginning in 1987, M1A1 tanks received improved armor packages that incorporated depleted uranium (DU) mesh in their armor at the front of the turret and the front of the hull. Armor reinforced in this manner offers significantly increased resistance towards all types of anti-tank weaponry, but at the expense of adding considerable weight to the tank, as depleted uranium is 1.7 times more dense than lead.

The first M1A1 tanks to receive this upgrade were tanks stationed in Germany, since they were the first line of defense against the Soviet Union. US-based tank battalions participating in Operation Desert Storm received an emergency program to upgrade their tanks with depleted uranium armor immediately before the onset of the campaign. M1A2 tanks uniformly incorporate depleted uranium armor, and all M1A1 tanks in active service have been upgraded to this standard as well, the added protection from the depleted uranium armor is believed to be equivalent to 24 inches (610 mm) of RHA. The strength of the armor is estimated to be about the same as similar western, contemporary main battle tanks such as the Leopard 2. In the Gulf War, Abrams tanks survived multiple hits at relatively close ranges from Iraqi Lion of Babylon tanks and ATGMs. M829A1 “Silver Bullet” APFSDS rounds from other M1A1 Abrams were unable to penetrate the front and side armor (even at close ranges) in friendly fire incidents as well as an incident in which another Abrams tried to destroy an Abrams that got stuck in mud and had to be abandoned.

The Leopard 2 is a German main battle tank (Kampfpanzer) developed by Krauss-Maffei in the early 1970s and first entering service in 1979. The Leopard 2 replaced the earlier Leopard 1 as the main battle tank of the German Army. Various versions have served in the armed forces of Germany and twelve other European countries, as well as several non-European nations. More than 3,480 Leopard 2s have been manufactured. The Leopard 2 first saw combat in Kosovo with the German Army and has also seen action in Afghanistan with the Danish and Canadian ISAF forces.

There are two main development batches of the tank, the original models up to Leopard 2A4 which have vertically-faced turret armour, and the “improved” batch, namely the Leopard 2A5 and newer versions, which have angled arrow-shaped turret appliqué armour together with a number of other improvements. All models feature digital fire control systems with laser rangefinders, a fully stabilized main gun and coaxial machine gun, and advanced night vision and sighting equipment (first vehicles used a low-light level TV system or LLLTV; thermal imaging was introduced later on). The tank has the ability to engage moving targets while moving over rough terrain.

The Leopard 2 utilizes spaced, multi-layered composite armour throughout the design. The Leopard 2A5 and A6 models utilize additional armour added to the turret front, and on hull and side skirts. Estimated levels of protection for the Leopard 2 range from 590 – 690 RHAe on the turret, 600 RHAe on the glacis and lower front hull on the Leopard 2A4, to 920 – 940 RHAe on the turret, 620 RHAe on the glacis and lower front hull on the Leopard 2A6 against kinetic projectiles. The mine-protected Leopard 2A6M adds an additional mine protection plate for the belly, which increases protection against mines and improvised explosive devices. All Leopard 2 variants after the Leopard 2A6 include spall liners on the inside of the tank, protecting the crew. The Leopard 2A6M CAN increases protection against rocket-propelled grenades (RPG’s) by including additional slat armour which serves to prematurely detonate such warheads harmlessly against the hull.

Two groups of 4 Wegmann 76 mm smoke mortars are mounted on either side of the turret and can be electrically fired either as single rounds or in salvos of four are mounted on most Leopard 2 models, with the exception of Dutch Leopard 2′s, which are instead equipped with a Dutch-designed smoke mortar system with six barrels on each side. Swedish Leopard 2′s utilize French GALIX smoke dispensers, similar to the system found on the French Leclerc.

The crew is also protected against Nuclear, Biological and Chemical (NBC) threats as well, as the Leopard 2 is equipped with a NBC overpressurization system which provides up to 4 mbar (0.004 kp/cm²) over pressure inside the vehicle.

The Leopard 2 is equipped with a fire protection system as well. Four 9 kg Halon fire extinguisher bottles are installed on the right behind the driver’s station. The bottles are connected to pipes and hoses and are activated automatically by the fire detection system, when temperatures rise above 180°F inside the fighting compartment, or manually via a control panel in the driver’s compartment. An extra 2.5 kg Halon fire extinguisher is also stored on the floor beneath the main gun.

The Merkava (Hebrew: Chariot) is the main battle tank of the Israel Defense Forces. Since the early 1980s, four main versions have been deployed. The “Merkava” name was derived from the IDF’s initial development program name.

It is optimized for crew survival and rapid repair of battle damage. Following the model of contemporary self-propelled howitzers, the turret assembly is located nearer the rear than in most main battle tanks. This gives the crew additional protection against a frontal attack by putting the engine between them and the attack. This arrangement also creates more space in the rear of the tank that allows increased storage capacity, as well as a rear entrance to the main crew compartment allowing easy access even under enemy fire. This allows the tank to be used as a platform for medical disembarkation, a forward command and control station, and an armored personnel carrier. The rear entrance’s clamshell-style doors provide overhead protection when off- and on-loading cargo and personnel.

It was reportedly decided shortly before the beginning of the 2006 Lebanon War that the Merkava line would be discontinued within four years.[3] However, on 7 November 2006, Haaretz reported that an Israeli General Staff assessment had ruled of the Merkava Mark IV that “if properly deployed, the tank can provide its crew with better protection than in the past,” and deferred the decision on discontinuing the line.

The Merkava was designed for crew survivability. Its armor is a laminate composite armor consisting of steel, nickel, and ceramic.[citation needed] This armor is spaced, with multiple layers welded on to deflect high explosive anti tank (HEAT) rounds. The Mark III Dor Dalet BAZ and the Mark IV were designed with more modern modular armour. Other protective features include a fire extinguisher system, and the engine and transmission being located in the front of the tank. This offers additional protection in the front, since any round that penetrates the frontal armor will be further slowed or stopped by the engine before it reaches the crew. This also allows for a squad of infantry to ride in the back of the tank. An emergency escape hatch is located in the rear of the tank for crew evacuation if the regular hatches are jammed by a blast. The hatch is so wide and large that infantry in the back of the tank, as well as the crew can use it. An additional safety feature is a a stretcher to evacuate a wounded crew member.

The Merkava Mark I was armed with a 105 mm M68 gun, as well as the Mark II. However, the Mark III, Mark III Dor Dalet BAZ kassag, and the Mark IV are all armed with an IMI 120 mm gun smoothbore gun.

Each model of the Merkava has two 7.62 machine guns for anti-infantry defense. Another unique feature, present in every model of the Merkava, is the 60 mm mortar.

Due to its heavy weight[citation needed], the tank’s road speed is considered slow when compared to that of other comparable tanks such as the Abrams or the Leopard 2. The turbocharged diesel engine, manufactured by Teledyne, generates 1,500 horsepower. The Mark IV’s top road speed is 40 miles per hour (64 km/h).[citation needed] On the other hand, the Mark IV’s off-road speed is faster than most comparable tanks, clocking in at 34 miles per hour (55 km/h) (to compare, the M1 Abrams has an off road speed of 30 miles per hour (48 km/h)).

In addition to increased off-road speed, the Merkava’s tracks have been specifically built to handle the extremely rough terrain such as the basalt rocks of the Golan heights, allowing the tank to move with ease through territory that would pose a considerable challenge to most tanks.

The Northrop Grumman B-2 Spirit (also known as the Stealth Bomber) is an American heavy bomber with “low observable” stealth technology designed to penetrate dense anti-aircraft defenses and deploy both conventional and nuclear weapons. Because of its considerable capital and operational costs, the project was controversial in the U.S. Congress and among the Joint Chiefs of Staff. During the late 1980s and early 1990s, the Congress slashed initial plans to purchase 132 bombers to just 21.

The cost of each aircraft averaged US$737 million in 1997 dollars ($1.01 billion today). Total procurement costs averaged US$929 million per aircraft ($1.27 billion today), which includes spare parts, equipment, retrofitting, and software support. The total program cost, which includes development, engineering and testing, averaged US$2.1 billion per aircraft (in 1997 dollars, $2.87 billion today).

Twenty B-2s are operated by the United States Air Force. Though originally designed in the 1980s for Cold War operations scenarios, B-2s were first used in combat to drop bombs on Serbia during the Kosovo War in 1999, and saw continued use during the wars in Iraq and Afghanistan. One aircraft was lost in 2008 when it crashed just after takeoff; the crew ejected safely.

The bomber has a crew of two and can drop up to 80 x 500 lb (230 kg)-class JDAM GPS-guided bombs, or 16 x 2,400 lb (1,100 kg) B83 nuclear bombs in a single pass through extremely dense anti-aircraft defenses. The B-2 is the only aircraft that can carry large air to surface standoff weapons in a stealth configuration. The program has been the subject of espionage and counter-espionage activity and the B-2 has provided prominent public spectacles at air shows since the 1990s.

The B-2′s low-observable, or “stealth”, characteristics give it the ability to penetrate an enemy’s most sophisticated anti-aircraft defenses to attack its most heavily defended targets. The bomber’s stealth comes from a combination of reduced acoustic, infrared, visual and radar signatures, making it difficult for opposition defenses to detect, track and engage the aircraft. Many specific aspects of the low-observability process remain classified. The B-2′s composite materials, special coatings and flying wing design, which reduces the number of leading edges, contribute to its stealth characteristics. The Spirit has a radar signature of about 0.1 m2.  Each B-2 requires a climate-controlled hangar large enough for its 172-foot (52 m) wingspan to protect the operational integrity of its sophisticated radar absorbent material and coatings. The engines are buried within the wing to conceal the induction fans and hide their exhaust.

The blending of low-observable technologies with high aerodynamic efficiency and large payload gives the B-2 significant advantages over previous bombers. The U.S. Air Force reports its range as approximately 6,000 nautical miles (6,900 mi; 11,000 km). Also, its low-observation ability provides the B-2 greater freedom of action at high altitudes, thus increasing its range and providing a better field of view for the aircraft’s sensors. It combines GPS Aided Targeting System (GATS) with GPS-aided bombs such as Joint Direct Attack Munition (JDAM). This uses its passive electronically scanned array APQ-181 radar to correct GPS errors of targets and gain much better than laser-guided weapon accuracy when “unguided” gravity bombs are equipped with a GPS-aided “smart” guidance tail kit. It can bomb 16 targets in a single pass when equipped with 1,000 or 2,000-pound (450 kg or 900 kg) bombs, or as many as 80 when carrying 500 lb (230 kg) bombs.

The B-2 has a crew of two: a pilot in the left seat, and mission commander in the right. The B-2 has provisions for a third crew member if needed. For comparison, the B-1B has a crew of four and the B-52 has a crew of five. B-2 crews have been used to pioneer sleep cycle research to improve crew performance on long sorties. The B-2 is highly automated, and, unlike two-seat fighters, one crew member can sleep, use a toilet or prepare a hot meal while the other monitors the aircraft.

As with the B-52 Stratofortress and B-1 Lancer, the B-2 provides the versatility inherent in manned bombers. Like other bombers, its assigned targets can be canceled or changed while in flight, the particular weapon assigned to a target can be changed, and the timing of attack, or the route to the target can be changed while in flight.

The prime contractor, responsible for overall system design, integration and support, is Northrop Grumman. Boeing, Raytheon (formerly Hughes Aircraft), G.E. and Vought Aircraft Industries, are subcontractors.

The original B-2 design had tanks for a contrail-inhibiting chemical, but this was replaced in the final design with a contrail sensor from Ophir that alerts the pilot when he should change altitude. Mission planning also considers altitudes where the probability of contrail formation is minimized.