The iconic McDonnell Douglas F-4 Phantom II was originally developed for the US Navy and entered service in 1960. Proving highly adaptable, it was soon adopted by the US Marine Corps and the US Air Force, and by the mid-1960s had become a major part of their air arms. The Phantom is a large fighter with a top speed of over Mach 2.2, and can carry more than 18,000lb of weapons on nine external hardpoints, including air-to-air missiles, air-to-ground missiles, and various bombs. The F-4 was used extensively during the Vietnam War, where it served as the principal air superiority fighter for the US Air Force, Navy, and Marine Corps and became important in the ground-attack and aerial reconnaissance roles later in the war. The aircraft continued to form a major part of US military air power throughout the 1970s and 1980s, being gradually replaced by more modern aircraft such as the F-15 Eagle, F-16 Fighting Falcon F-14 Tomcat and the F A-18 Hornet. The F-4 Phantom II remained in use by the US forces in the reconnaissance and Wild Weasel roles in the 1991 Gulf War.