 Unit commanders could also be awarded the medal for the exemplary conduct of the unit as a whole.Also, U-boat commanders could qualify for sinking 100,000 tons of shipping and "Luftwaffe" pilots could qualify for accumulating 20 "points" (with one point being awarded for shooting down a single-engine plane, two points for a twin-engine plane and three for a four-engine plane, with all points being doubled at night).It was issued from 1939 to 1945, with the requirements being gradually raised as the war went on.