The M1 Abrams is a third-generation American main battle tank designed by Chrysler Defense (now General Dynamics Land Systems) and named for General Creighton Abrams. Extensive improvements have been implemented to the latest formerly designated M1A2 System Enhancement Package version 3 or SEPv3 and M1A2 SEPv4, respectively versions such as improved composite armor, better optics, digital systems and ammunition. The Abrams was due to be replaced by the Future Combat Systems XM1202 but due to its cancellation, the U.S. military has opted to continue maintaining and operating the M1 series for the foreseeable future by upgrading with improved optics, armor and firepower. The M1 Abrams entered service in 1980 and currently serves as the main battle tank of the United States Army and formerly the Marine Corps.