The Leopard 2 was the first Western third generation tank to enter service, in 1978, and has since consolidated as one of the finest tanks in the world thanks to its near-perfect mix of armament, protection and mobility, and its ability to be continuously upgraded throughout its more than three decades of life. The Leopard 2 was developed as a result of the failure of the MBT-70 program between the US and West Germany, after which the Germans went ahead with their own MBT design. The Leopard 2's design prioritizes crew survivability; both the engine (in the rear of the hull) as well as the ammunition stowage (in the rear of the turret) are separated from the crew with fireproof bulkheads with additional blow-out panels to disperse the explosion. Armor is of an unspecified composite type believed to consist of various layers of spaced steel with additional non-metal materials, with additional armored skirts at the front. The hull floor is also sloped to provide additional protection against mines. Upgraded Leopard 2s would feature additional armor modules on the turret which give it a characteristic arrowhead shape, and they are also believed to incorporate titanium and tungsten in the composite armor mix. As a result of the additional weight, a powerful 1,500-hp diesel engine allows it to obtain greater speeds than the much lighter Leopard 1 that it replaced. The Leopard 2 was the first Western tank to be equipped with the outstanding Rheinmetall 120-mm Rh-120 L/44 smoothbore which was later used on the US M1 (among others) as well. It was primarily equipped with tungsten APFSDS-T rounds. Newer variants feature a lengthened L/55 gun which allows for higher muzzle velocities and penetration power. The Leopard 2 is equipped with advanced electronics including a digital fire control system, laser rangefinder, thermographic camera, thermal sights, as well as an advanced gun stabilization system that allows accurate firing on the move. There is also NBC protection and can be equipped with a snorkel for deep fording. When introduced, the Leopard 2 gave the West German army a tank superior to any Soviet tank then in service, and continuous upgrades have allowed it to keep its edge against any likely rival. The Leopard 2 has had considerably better export success than the M1, with the large German (and Dutch) stocks left over after the end of the Cold War largely sold off abroad. It is currently the main battle tank of Austria, Canada, Chile, Denmark, Finland, Greece, Indonesia, Netherlands, Norway, Poland, Portugal, Qatar, Singapore, Spain, and Turkey. Notably it was also adopted by Sweden and Switzerland which had previously fielded mostly locally-designed tanks. In contrast to the M1 and Challenger 1/2 which have been battle-tested in Iraq, the Leopard 2 has much more modest combat experience, with only occasional action in Afghanistan against the Taliban and Turkish units in Syria against ISIS where a few older variants were knocked out by ATGMs. Nevertheless, it has yet to engage an enemy tank in combat. Despite some initial reluctance by German authorities, large numbers of Leopard 2s have now been pledged by Germany along with other NATO countries to Ukraine and it is likely that they will see their first true test in a modern battlefield sometime in 2023.

Initial prototypes of the Leopard 2 were completed between 1972 and 1974, some of which had an earlier Rheinmetall 105-mm gun. A pre-production variant known as the Leopard 2AV (Austere Version) subsequently competed with the XM1 prototype in 1976 for a US Army contract but lost out to the local design. Following the initial production Leopard 2, there were only minor differences between the next three batches which were nevertheless designated as Leopard 2A1, A2 and A3, one notable change was the addition of a gunner's thermal sight which was not available in the initial batch. The Leopard 2A4 became the definitive variant of the original series, incorporating titanium/tungsten armor for the flat turret front, an all-digital fire control system and the ability to carry additional ammunition types. It was the most widely produced version of all, and most early models were eventually brought up to A4 standard. The subsequent Leopard 2A5, initially referred to as the Leopard 2 (Improved), featured a radical redesign of the turret, with spaced add-on armor giving extra protection against both kinetic and chemical rounds, as well as all-electric controls. This was followed by the Leopard 2A6 which adds a longer caliber (L/55) version of the Rheinmetall Rh-120 gun as well as improved mine protection. A separate urban warfare kit (known as PSO or Peace Support Operations) can also be added. Further enhancements resulted in the Leopard 2A7 which includes a new integrated combat management and information system known as IFIS, an auxiliary power unit, and additional belly armor. An export version known as the Leopard 2A7+ is optimized for urban combat with additional armor modules, improved situational awareness, and a remote-controlled weapons station which could carry a machine gun or a GMS automatic grenade launcher. The latest version adopted by the Germany army is the Leopard 2A7V which uses an improved Rh-120 L55A1 gun and further armor modules which had previously been mostly used in export versions. Other export versions may feature numerous differences or enhancements from their German counterparts, but otherwise tend to be based on the A4-A7 variants. Swedish versions are known as Strv 122 while Swiss versions are designated Pz 87. Non-combat versions include the Büffel armored recovery vehicle, Legun bridge layer, and the Kodiak combat engineering vehicle for the Swiss Army.