The K1 is a South Korean 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.