The Leopard 2 was developed in response to a demand for a new main battle tank, which the Bundeswehr announced as early as the beginning of the 1960s. The new vehicle was to replace the Leopard 1 tanks of the West German army. Initially, cooperation with American companies (such as Chrysler) was started in a project called MBT-70. However, after a few years, the cooperation was discontinued and further work focused solely on German companies. Despite a very long process of analytical, research, and experimental work, which lasted almost 15 years, the Leopard 2, which was introduced in this line in 1979, turned out to be revolutionary and surpassed the then Soviet designs. Many analysts consider it the first third-generation tank in history, including the M1 Abrams, the French Leclerc, or the much later Russian T-90 tanks. Thanks to its powerful 1,500 hp engine, the Leopard 2 is mainly characterized by unprecedented—before 1979—mobility and maneuverability in this class of tanks. It also has very good armor, using composite materials and an FCS (fire control system). It was also armed with the excellent Rh-M-120 gun, which became the standard for many NATO countries in the 1980s and 1990s. Several versions of the Leopard 2 tank were created in serial production, two of which deserve special attention: the A4 and A6. The A4 version, which first appeared in 1985, has a greatly improved and enhanced FCS compared to previous versions, as well as an improved turret and front armor hull. It is also the most widely exported version. At the beginning of the 21st century, the A6 version was created, which mainly received the Rh-M-120 gun with a significantly longer barrel (L/55), which significantly improved its penetration capability. The latest development version of the Leopard 2 tank is the A7 version, which entered Bundeswehr service in 2014. Thanks to its very high combat value, the Leopard 2 has been exported to many countries, including Austria, Chile, Denmark, Finland, Greece, Spain, the Netherlands, Norway, and Poland, which has 247 tanks of this type in A4 and A5 versions.