During the Vietnam War, it quickly became apparent that troop carrying helicopters required some kind of armed escort. The AH-1 Cobra was intended to be a stopgap measure to meet this need while a new aircraft could be designed. As a result, the AH-1 had many parts in common with the UH-1 Huey. However, the Cobra was such a success that it is still in use today and the proposed replacement, the AH-56 Commanche, was canceled. The AH-1W is a navalized twin engine version of the Cobra and is used exclusively by the U.S. Marine Corps for close air support of ground troops.