 This requirement has been underscored by the appearance of the Russian T-90 main battle tank.Even the elongation of current gun tubes, such as the new German 120 mm L/55, which was introduced by Rheinmetall is considered only an interim solution as it does not offer the required increase in muzzle velocity.Even advanced kinetic energy ammunition such as the United States' M829A3 is considered only an interim solution against future threats.