On July 21 Château-Thierry was given up by the Germans, and the pursuing Allies, French and American, drove the enemy beyond the highroad to Soissons, and threatened the only highway of retreat, as well as the German stores. The supply-centre within the salient was Fère-en-Tardenois, and it was being raked by Allied guns from both sides of the salient. The character of the fighting changed again, so that again it was impossible to make sure if Von Boehm intended to stand somewhere north of the Marne and put up a fight, or if he intended to make all speed back to a straight line between Soissons and Rheims. The resistance was by machine-gun, so that Americans, having their first big experience with the enemy, insisted that he had nothing but machine-guns to trust to. It is, of course, possible that the crown prince and Von Boehm knew no more than anybody else whether they were going to clear out, men and supplies, or whether they would stop again and fight face foremost. On July 22 the German command answered the question at least partially. On a line well above the Marne, they brought the big guns into play, and poured in shock troops. Airplanes from the Allied lines discovered, however, that the Germans were burning towns and store-houses for many miles behind the line. The pressure on the Germans was being brought from the south, where the Americans were six or seven miles above Château-Thierry, and from the west and north, where the Franco-American troops were flaying the exposed side. The stiffened resistance and the German artillery slowed, but could not stop, the Allied advance. The eastern side of the salient, from the Marne to Rheims, bore some desperate blows, but did not give way. As the pincers closed in, at the top of the salient, the German command appeared to go back to its original plan of attacking Rheims from the south. This was the side on which British and Italian troops were co-operating with the French, and the German command got for its pains in that direction a counter-attack which narrowed the distance from battle-line to battle-line across the top of the salient. The French menaced Fère-en-Tardenois, the German base of supplies. Allied aviators bombed these stores, the long-range guns pounded at them, and what with these and the conflagrations started defensively by the Germans the Marne salient was a caldron which turned the skies blood-red. On July 24 the ground gained all along the line averaged two miles. The British southwest of Rheims made a damaging curve inward, and the shove around the other two sides was fairly even.