Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The Rheinmetall 120-millimeter (4.7 in) gun is a smoothbore tank gun designed and produced by the German Rheinmetall-DeTec AG company. It was developed in response to Soviet advances in armor technology and development of new armored threats. With production beginning in 1974, the first version of the gun, known as the L/44, was used on the German Leopard 2, and was soon license produced to be used on tanks such as the American M1A1 Abrams tanks. It has also been exported to South Korea and Japan, as well as nations which have procured the Leopard 2 and the M1 Abrams. Rheinmetall''s 120-millimeter (4.7 in) L/44 tank gun has a length of 5.28 meters (5.77 yd), while the gun system weighs approximately 3317 kilograms (7310 lb). However, by 1990 the L/44 was not considered powerful enough to deal with modernized Soviet armor, such as the T-80B, which stimulated an effort by Rheinmetall to develop a better main armament.