It is impossible not to admire the way in which the German general in command observed and attempted to profit by any gap in the British line. It has already been shown how he tried to push his column between the two divisions of the First Corps and was only stopped by the deployment of the 3rd Brigade. Later, an even fairer chance presented itself, and he was quick to take advantage of it. The advance of the Guards Brigade to the Ostel ridge had caused a considerable gap between them and the nearest unit of the Second Corps, and also between the First Corps and the river. A German attack came swarming down upon the weak spot. From Troyon to Ostel, over five miles of ground, Haig's corps was engaged to the last man and pinned down in their positions. It was not possible to fill the gap. Not to fill it might have meant disaster--disaster under heavy shell-fire with an unfordable river in the rear. Here was a supreme example of the grand work that was done when our cavalry were made efficient as dismounted riflemen. Their mobility brought them quickly to the danger spot. Their training turned them in an instant from {174} horsemen to infantry. The 15th Hussars, the Irish Horse, the whole of Briggs' 1st Cavalry Brigade, and finally the whole of De Lisle's 2nd Cavalry Brigade, were thrown into the gap. The German advance was stayed and the danger passed. From now onwards the echelon formed by the units of the First Corps ended with these cavalry brigades near Chavonne to the immediate north of the river. The Third Division of the Second Corps, being on the immediate left of the operations which have been already described, moved forward upon Aizy, which is on about the same level as Ostel, the objective of the Guards. The 8th (Doran's) Brigade moved north by a tributary stream which runs down to the Aisne, while the 9th (Shaw's) tried to advance in line with it on the plateau to the right. Both brigades found it impossible to get any farther, and established themselves in entrenchments about a mile north of Vailly, so as to cover the important bridge at that place, where the 7th Brigade was in reserve. The three Fusilier regiments of the 9th Brigade all lost heavily, and the Lincolns had at one time to recross the river, but recovered their position. The attack made by the Fifth Division near Missy was held up by a very strong German position among the woods on the Chivres heights which was fronted by wire entanglements. The regiments chiefly engaged were the Norfolks and Bedfords of the 15th Brigade, with the Cornwalls and East Surreys of the 14th Brigade, the remains of the Cheshires being in close support. They crossed the wire and made good progress at first, but were eventually brought to a stand by heavy fire at close range from a trench upon their right front. It was already dusk, so the {175} troops ended by maintaining the position at Missy and Ste. Marguerite, where there were bridges to be guarded.