I slept for about two hours that night in one of the lower bunks. In the upper tier above me was the body of a dead German. The Germans had built this tunnel with two objects in mind: first, to enable them to bring forward reinforcements from the_ Zwischen Stellung_ trench to their front line, which was a distance of 560 yards, without exposing them to our observation and artillery fire and, secondly, that they could also withdraw their men from the front and support trenches without suffering any casualties. The Germans had made every arrangement with a view to the comfort of both their officers and men. Electric light had been generated from Vimy Village. The tunnel could shelter comfortably one battalion. Ventilation shafts ran up from it to the surface, and there were chambers or rooms off the main passageway to serve the purposes of a garrison that might be isolated. Commander's post, telephones, temporary hospital, baths with hot and cold water installation, and depots for ammunition and food were here. It can readily be seen that the Germans expected to remain on the spot, but our New World troops upset their calculations. One day on the Western front there was a duel in the air. It looked as if the old days were to come back again, when the armies would cease fighting and watch their respective champions in single combat. This fight resulted in the death of Immelman, at that time Germany's most distinguished aviator. It was in truth a duel, no chance meeting of men determined to slay one another, but a battle following a regular challenge and fought by prearrangement and without interference from either side. This air battle was witnessed with the deepest interest by the men of both armies who were crouched in the trenches and separated only by a few yards at No Man's Land. The fire of the anti-aircraft gun on both sides was stilled. Captain Ball, the youthful English pilot who was recently killed after a series of winning battles in the air, was the victor. The story of the duel, which was one of the most sensational events of the war, was told in a letter written to me by a friend of mine who was one of the eye witnesses of the fight. One morning Captain Ball, who was behind our sector, heard that Immelman was opposite. "This is the chance I have been waiting for. I am going to get him," declared Ball. His friends tried to dissuade him by saying the story of Immelman's presence probably was untrue. Ball would not listen. Getting into his machine, he flew over the German lines and dropped a note, which read: "Captain Immelman: "I challenge you to a man-to-man fight to take place this afternoon at two o'clock. I will meet you over the German lines. Have your anti-aircraft guns withhold their fire while we decide which is the better man. The British guns will be silent. "(Signed) Ball." About an hour afterwards a German airman swung out across our lines and dropped Immelman's answer: "Captain Ball: