The AH-1J Sea Cobra was developed for the US Marine Corps as a twin engine variant of the AH-1 Cobra based on the USMC's desire for improved safety and redundancy for over-water operation. It has a Pratt and Whitney Twinpac T400 engine (two 900-hp turboshaft engines coupled together), a new nose turret gun with a three barrel XM197 20mm cannon, and other improvements.