The morning set for the opening of the St. Mihiel offensive, Sept. 12, 1918, the clouds hung low and the weather was such that ordinarily it would have been regarded as altogether unfit for flying. But Luke was not to be deterred by it. He was off at dawn in quest of enemy planes or balloons and after many vain explorations he finally discovered a German balloon at the extreme right of the American sector, but operated against a portion of the line allotted to other flyers. He returned to his aerodrome, and on reporting the balloon learned that it had been doing great damage by an enfilading fire, but that it had been attacked repeatedly without success both by American and French aviators. Luke offered to destroy the balloon and set off with Lieut. Fritz Wehner, his flying partner. The statement of eye-witnesses from the ground was that Luke dived suddenly out of the clouds taking the balloon wholly by surprise, but the balloon-gun which he was handling for the first time jammed when he attempted to discharge it. He rose into the clouds, got the gun free, immediately dived again and fired the heavy incendiary bullet that sent the balloon down in flames. DOWNED THREE BALLOONS IN ONE DAY Two days later he sent another balloon flaming down in somewhat more exciting circumstances. While he was speeding with an escort of other pilots, to attack three enemy balloons operating at an unusually low altitude, his escort became engaged with a formation of Fokkers. This would have made it seem to many pilots unwise to proceed with the attack; but Luke took advantage of the fight above to dive down and begin the assault on one of the balloons which, after several attempts, he succeeded in shooting down, though machine bullets and anti-aircraft shells and flaming onions were showered about him. As the balloon fell burning, Luke flew down to close range and turned loose his machine gun on the Huns on the ground with the desired result of many casualties. When he got back home he found that his machine was so full of bullet holes that a very few more taps would have weakened it enough to bring it down in collapse. But within five minutes he was in another machine and begging leave to go on a further quest. At 5 o’clock that afternoon he sent down the second balloon in flames. Later he discovered attempts being made to send up another balloon north of Verdun; he hastened back to his squadron and asked to be ordered out at dusk to surprise and destroy the big bag. He left with instructions not to descend on the balloon until 7.50 (that being for the benefit of his protective escort who would follow him down a few moments later). Precisely at 7.50 the watchers on the aerodrome saw the balloon flare in the darkness and fall to the ground.