The MiG-15 was one of the first successful jet fighters to incorporate swept wings to achieve high transonic speeds. In aerial combat during the Korean War, it outclassed straight-winged jet day fighters, which were largely relegated to ground-attack roles.
An improved variant, the MiG-15bis ("second"), entered service in early 1950 with a Klimov VK-1 engine, plus minor improvements and upgrades. Some "bis" aircraft also adopted under-wing hardpoints for unguided rocket launchers or 50–250 kg (110–550 lb) bombs.
