Formed in July 1942, the Pathfinder force was the corps d’élite of Bomber Command, tasked with marking targets and leading bomber formations to the right place at the right time. And the best of the force formed the crews of the master bombers, the aircraft in charge of the whole attack. It took nerves of steel for the crew to linger long high over the target area, often for hours, in constant fear of attack from fighters or flak.