Saturday, 23rd March, dawned again in fog, and from an early hour it became clear that the position allotted to Congreve could not be held. That day von der Marwitz began the most dangerous movement of all—the attempt to drive a wedge between the Third and Fifth Armies. Very early in the morning he attacked the Green Line, which was held by details of the 9th Division. The advance was checked; but the position was clearly untenable, and the South African details, under Lieutenant-Colonel Young, fell back to Bouchavesnes, where they again came under Dawson’s orders. That day the South Africans were nominally in reserve, holding a position in echelon on the right flank of the 27th Brigade. But a wavering front, faced by preposterous odds, called every man into the fight, and presently the Brigade was in the front line again on the right of the 27th, endeavouring to maintain touch with the 21st Division, which was compelled to retire by the withdrawal on its right from the Péronne bridgehead. During the morning Dawson fell back from Moislains, and took up ground about midday on the ridge south-west of that village, overlooking the Tortille River, where, during the afternoon, he was heavily shelled. Once again came the old menace on the right wing. The 21st Division, itself outflanked by the withdrawal farther south, was again retiring, and presently Dawson’s flank was in the air, and the enemy in the immediate south was more than a mile behind his front. He had five tanks as a flank-guard, and he endeavoured to fling out posts as a defensive flank across the Péronne-Arras road. An officer and twenty men were sent to occupy the cutting on the summit of the ridge overlooking Mont St. Quentin. All afternoon the enemy poured down the slopes along the Péronne-Nurlu road, and before dark fell he had occupied Moislains and Haute-Allaines. General Tudor visited Dawson in the evening. The situation of the whole 9th Division under von der Marwitz’s thrust had grown desperate. It was holding an impossibly long line, and a gap had opened between its left and Fanshawe’s V. Corps in the Third Army, of which the enemy had promptly taken advantage, in spite of gallant attempts to fill the breach made by the 47th London Division and a Brigade of the 2nd. On its right it was out of touch with the 21st Division; so that that evening it was holding a salient of high ground with both flanks hopelessly in the air. There was no other course but to fall back, especially as the retirement of the 21st Division was by no means at an end. The 1st Regiment had been moved from the left of the South African Brigade to strengthen the right flank, but it could not hope to fill the breach, the more as the enemy was pressing hard from Moislains against this weak spot.