 On the day of the raid, Greisert and other elements of his Jagdschwader engaged Boston bombers and their escorts as they conducted a bombing raid over the harbor facilities at Cherbourg, shooting down one of their number.The German fighters were returning to base just as the Lancaster force was passing near their airfield.As the German aviators approached their air base at Beaumont-le-Roger they caught sight of the British bombers flying at high speed and very low level a short distance away.