The U.S. Air Force’s A-10 is an ugly, low-flying, slow-moving beast of an aircraft known affectionately by the troops as the Warthog. But even as the flying tank gets ready to shred ISIS terrorists to pieces over Iraq and Syria with its massive 30mm cannon—firing depleted uranium shells the size of a Coke bottle—it hides a dark secret: an unrepentant Nazi fighter pilot helped to develop the ungainly warplane.

Engineer Pierre Sprey, a former Pentagon procurement official who helped design the A-10, confirmed to The Daily Beast that none other than legendary Luftwaffe Colonel Hans-Ulrich Rudel was consulted to develop the Warthog.

“While we were readying the airplane and gun for full scale production, the 30mm gun program manager, Col. Robert Dilger, invited Rudel to lead a symposium in DC attended by several hundred engineers, analysts, tacticians and intel types on all aspects of CAS [close air support] operations in combat,” Sprey told the Daily Beast. “For lots of them it was eye-opening. I translated for Rudel who spoke very little English.”