Major Merse, the commanding officer, invited us to his headquarters. They were in a house of stone and mud, from which projected a wooden platform. When any one appeared upon it he had the look of being about to make a speech. The major asked us to take photographs of Gravec and send them to his wife. He wanted her to see in what sort of a place he was condemned to exist during the winter. He did not wish her to think of him as sitting in front of a cafe on the sidewalk, and the snap-shots would show her that Gravec has no cafes, no sidewalks and no streets. But he was not condemned to spend the winter in Gravec. Within the week great stores of ammunition and supplies began to pour into it from Krivolak, and the Gate of Iron became the advanced position, and Gravec suddenly found herself of importance as the French base. To understand this withdrawal, find on the map Krivolak, and follow the railroad and River Vardar southeast to Gravec. The cause of the retreat was the inability of the Serbians to hold Monastir and their withdrawal west, which left a gap in the former line of Serbians, French, and British. The enemy thus was south and west of Sarrail, and his left flank was exposed. On December 3, finding the advanced position at Krivolak threatened by four divisions, 100,000 men, General Sarrail began the withdrawal, sending south by rail without loss all ammunition and stores. He destroyed the tunnel at Krivolak and all the bridges across the Vardar, and on his left at the Cerna River. The fighting was heavy at Prevedo and Biserence, but the French losses were small. He withdrew slowly, twenty miles in one week. The British also withdrew from their first line to their second line of defense. Demir-Kapu, meaning the Gate of Iron, is the entrance to a valley celebrated for its wild and magnificent beauty. Starting at Demir-Kapu, it ends two kilometres north of Gravec. It rises on either side of the Vardar River and railroad line, and in places is less than a hundred yards wide. It is formed of sheer hills of rock, treeless and exposed. But the fame of Gravec as the French base was short-lived. For the Serbians at Monastir and Gevgeli, though fighting bravely, were forced toward Albania, leaving the left flank of Sarrail still more exposed. And the Gate of Iron belied her ancient title. With 100,000 Bulgars crowding down upon him General Sarrail wasted no lives, either French or English, but again withdrew. He was outnumbered, some say five to one. In any event, he was outnumbered as inevitably as three of a kind beat two pair. A good poker player does not waste chips backing two pair. Neither should a good general, when his chips are human lives. As it was, in the retreat seven hundred French were killed or wounded, and of the British, who were more directly in the path of the Bulgars, one thousand.