The obsolescence of the AD/A-1 Skyraider attack aircraft led to the search for a new plane able to satisfy both US Navy (USN) and US Marine Corps (USMC) requirements. Aside from the type of engine, the new plane was to be capable of all-weather operations. Grumman was one of eleven companies that sent their designs for selection, and Grumman's design was selected in January 1958 as the YA2F-1. Following development and testing, the YA2F-1 was accepted into the US Navy in February 1963 as the A-6 Intruder. Following experiences in the Vietnam War, the A-6 went through multiple variants featuring improvements or for specialized roles. The A-6E was introduced in December 1972 with better navigation, attack, and radar equipment. It featured another enhancement in 1979 with the Target Recognition and Attack Multi-sensors (TRAM) system, which enabled better targeting abilities for improved munition accuracy. The A-6E Intruder and its variants continued serving the US Navy in most combat operations from the Vietnam War onwards, including the 1991 Gulf War. All Intruders were retired by February 1997.