This fellow is the pilot of General Rosemeyer's helicopter pilot--wait, what, a helicopter in World War II? Yes, odd as it seems, there were rotary-wing aircraft late in the war. The Nazis had some experimental aircraft, and perhaps this is meant to be one of those (even though it's an American Bell 47 with Swastikas painted on it).
Anyway, our pilot friend here flies Rosemeyer to the Schloss Adler to meet with, and interrogate, captured American General Carnaby. When Smith and Schaffer infiltrate the castle disguised as German officers, they see the helicopter and become worried it might be used to fly Carnaby out. They decide to cripple it.
Deciding that trying to tinker with the machine in a courtyard full of soldiers, they decided instead that the best way to cripple the copter is to kill its pilot. A trap is laid. Smith informs the pilot that "the commandant" wants him on the line. The pilot dutifully heads to the telephone room, and finds the operator sitting upright in his chair, unmoving (having been shot by Schaffer). Nobody is more surprised than him when Schaffer steps out from hiding, and seizes him from behind. The American's hand clamps over his mouth, and drives his knife into his back. The dead pilot hits the floor just as Smith enters to find his partner wiping the blood off of his blade.
"Well, that was quick," Smith observes.
"Fear lent him wings, as the saying goes," quips Schaffer.