The K1 is a South Korean third-generation main battle tank in use with the Republic of Korea Armed Forces, developed by Hyundai Precision (later Hyundai Rotem). The vehicle's early design work was based on General Dynamics' M1 Abrams, with some noticeable differences including a combined system of hydropneumatic suspension and torsion bars, and a river-crossing fording kit, to meet the required operational capability that was specific to combat operations in the mountainous and swampy terrain of the Korean Peninsula. The K1A1 entered service in 1999, upgraded with a 120mm smoothbore gun, and outfitted with more modern electronics, ballistic computers, and fire control systems developed by Samsung Electronics. Hyundai Rotem produced 1,511 K1 and K1A1 tanks between 1985 and 2010.