Shortly afterwards the mist cleared and the awkwardness of the situation became more apparent. The 18th Division were being pressed back towards Villequier-Aumont, and the left flank was entirely in the air, while the constant pushing of small highly trained bodies of the enemy was enabling them to progress along the Oise marshes on the right. Vouel itself was strongly occupied, and troops were massing for attack. By 12 noon the position was no longer tenable. The enemy was advancing frontally and from both flanks, and Lieut.-Col. Dann ordered a withdrawal on to the Green line. This was a partly dug position which formed a portion of the Rear Zone and was held by troops of the 6th Dismounted Cavalry Brigade and the 18th Entrenching Battalion, on a line east of Noureuil and Viry-Noureuil from the St Quentin Canal to the Vouel-Villequier Road. The withdrawal to the Green line from the Vouel position averaged about 1500 yards, and so hard were the enemy pressing that some platoons had to fight their way back. An attempt was made by the French machine-gunners in the Vouel line to cover the Battalion's withdrawal, but this was not effective and, together with several of our own men, they were captured. The situation was now critical. The falling back of the 18th Division on the left revealed a gap between the Vouel-Villequier Road and Frières Wood of which the enemy was not slow to take advantage, and there appeared every likelihood that the 173rd Brigade would be cut off from the 18th Division and rolled up against the St Quentin Canal. To meet this threat the left flank of the Green line position, consisting of troops of the Dismounted Brigade and details of the 8th Londons, was thrown back and extended towards Villequier-Aumont in an attempt to gain touch once more with the 18th Division. This line was thin, and under the continued German pressure it suffered severely. During the afternoon the enemy thrust south again and entered Noureuil, thus driving a wedge behind the flank of the Green line troops. A glance at the map will show that a further withdrawal was inevitable if the whole Brigade was not to be rounded up. This began about 6 p.m. and the troops, including all that was left of the fighting ranks of the 2/4th Londons, about 120 all told under Capt. Askham, fell back to a position west of Viry-Noureuil, which village was yielded to the enemy.