The T-84 is a Ukrainian main battle tank (MBT), based on the Soviet T-80 main battle tank introduced in 1976. The T-84 was first built in 1994 and entered service in the Ukrainian Armed Forces in 1999. The T-84 is based on the diesel-engined T-80 version, the T-80UD. Its high-performance opposed-piston engine makes it a fast tank, comparable to other modern MBTs with a power-to-weight ratio of about 26 horsepower per tonne (19 kW/t). The T-84 Oplot is an advanced version incorporating an armoured ammunition compartment in a new turret bustle. Ten of these entered Ukrainian service in 2001. The T-84-120 Yatagan is a prototype model intended for export, mounting a 120 mm gun capable of firing standard NATO ammunition and guided missiles.