Originally designated as the F-110 Spectre, manufactured by McDonnell Douglas, the F-4 Phantom II is a two-seat, twin-engine, long range, long range interceptor fighter-bomber, which was originally developed for short take off use by the US Navy. Entering service in 1960, it proved to be very versatile and was eventually commissioned by the US Marine Corps as well as the US Air Force. It soon became a work horse in each service's respective air wing.
The F-4, or "lead sled" as it was referred to by its pilots, It can carry up to 18,650lbs of weapons on nine different external handpoints. This generally included GP bombs, cluster bombs, Laser and TV guided bombs, rocket pods (up to 6 carrying 18X 68MM SNEB rockets), air-to-ground missiles, anti-runway weapons, anti-ship missiles, targeting pods, recon pods, and tactical nuclear weapons. Weapons could also be replaced with external fuel pods for long range sorties.
Though the F4 had proven its air superiority time and time again, it had one major weakness: lack of an internal cannon. Many times during the air combat in the Vietnam conflict, pilots found themselves too close for short range missiles. Though they caused severe drag at high speeds, many pilots requested external SUU-16 gun pods containing a 20mm (.79in.) M61 Gatling cannon, as they proved to be more effective in many combat situations.