Explanation: When the Americans learned of the Soviet Mig-25 'Foxbat', the US was certain that the high-speed jet shown by the Soviets was, due to its design and the classified nature of its technical details, an ultra-maneuverable ultra-fast fighter jet, and in response, poured money into the F-15 'Eagle' to make it a weapon that could compare to its Soviet counterpart!
Some ten years later a defector landed with a Mig-25 and handed it over to Western intelligence. Turns out, it wasn't maneuverable at all, or a fighter, for that matter. It was an interceptor made for catching nuclear bombers, and had all the maneuverability of stiff cardboard. Very fast, though! C'est la vie!
He added, "Only when McDonnell Douglas later went to analyze it, they said, OK, the F-15 has a very wide [lifting] body; you fly fast enough and you're like a rocket. You don't need wings."