The F-15 was born from the difficult lessons learned during the Vietnam War. In the late 1950s, Air Force planners were confident that the advent of powerful new radars and long-range air-to-air missiles had rendered close-range aerial combat a thing of the past. So fighter jets like venerable the Mcdonnell Douglas F-4 Phantom were not engineered to be light or agile like their predecessors. Instead, they were designed to be heavily-loaded with missiles and carry powerful radars. Their pilots were no longer trained to dogfight, as they would engage the enemy at great distances, well beyond visual range.
Credit Dark Skies