The Fifth Army, under General Sir Hubert Gough, consisting of the IIIrd, XVIIIth, XIXth and VIIth Corps, held an extended front of some forty-two miles from the Oise to Gouzeaucourt, where the Third Army, under General the Hon. Sir Julian Byng, continued the line to the Scarpe. The XVIIIth Corps held a line facing St Quentin from Urvillers to Gricourt, with the 36th Division on the right, the 30th opposite St Quentin, and the 61st on the left. On the right of the 36th Division was the 14th Division of the IIIrd Corps. On the left of the 61st Division was the XIXth Corps. The 20th Division, if called upon to support this line, was to move forward ready to man the rear zone defences between the Somme and the Omignon river from St Simon to Trefcon, sending a brigade of artillery to each of the 36th and 30th Divisions.
At 4.40 A.M. on the 21st of March the enemy opened an intense bombardment along practically the whole front of the Fifth and Third Armies, using a great quantity of gas shells. The infantry attack, launched in a thick fog after several hours of this bombardment, developed on the XVIIIth Corps front about 10.30 A.M.
By noon the line had been penetrated at various points, although on all parts of the front isolated detachments held out most gallantly. The infantry of the 20th Division was ordered at 1 P.M. to concentrate behind the rear zone defences, and the artillery brigades moved forward to their allotted divisions, the 91st (Lieut.-Colonel Erskine) to the 36th Division and the 92nd (Lieut.-Colonel Balston) to the 30th.
In the course of the day the enemy pushed forward, particularly on the right of the Corps line, where by 3 P.M. the situation had become critical. The 61st Brigade (Brig.-General Cochrane) was ordered therefore to man the bridge-heads at St Simon and Tugny immediately on arrival in that area. Pressed on the front and outflanked on the right, the 36th Division retired during the night south of the Somme. The 61st Infantry Brigade and the 91st Field Artillery Brigade covered this retirement, and from that time came under the orders of the 36th Division. Here we will leave them for the moment in order to trace the movements of the rest of the 20th Division during the following four days.
On the left the Germans had penetrated the line at the junction of the XVIIIth and XIXth Corps and at Roupy, and had gained a footing in Grand Seraucourt. The 60th Brigade (Brig.-General Duncan) therefore pushed out covering troops on the defensive line from the Somme to Vaux, and as troops of the 30th Division were retiring on the left, the 59th Brigade (Brig.-General Hyslop) manned the defences between Vaux and the Corps left boundary at Trefcon. The 92nd Field Artillery Brigade under the 30th Division was in action south of Fluquières, covering a line between Roupy and Savy.
All details were formed into a Divisional Reinforcement Battalion under Major Storr, second in command of the 12th King’s, and moved to a position between Matigny and Douilly. The 11th D.L.I. concentrated at Golancourt and sent “D” Company to reinforce the 61st Brigade. Divisional Headquarters came forward to Ham.
This was the situation on the night of the 21st, when the enemy had advanced west and south-west of St Quentin for a distance of about three miles. Although he had made an important advance along the whole front, he had not yet broken through the battle zone.
Taking advantage of the thick mist which still hung over the country, the enemy worked down the St Quentin Canal on the 22nd towards Happencourt. This threatened the right flank of the 60th Brigade. The 59th was therefore withdrawn from the rear zone defences between Vaux and Trefcon, leaving there only a skeleton force, and assembled in the Germaine—Foreste area, ready to launch a counter attack, if necessary, towards the south-east. But at 5.50 P.M. the enemy turned the left flank of the Corps north of Holnon Wood, driving back the 61st Division, which retired towards the Somme. To meet this new situation the 59th Brigade occupied a previously sited rearguard position between Douilly and Lanchy.
The 60th Brigade was attacked after heavy shelling at 3.50 P.M. Although their front line was driven back for a short distance, all battalions withstood the attack until they were ordered to withdraw. The 6th K.S.L.I. (Lieut.-Colonel Welch) on the right made a fine stand west of Happencourt with the enemy on both flanks; two companies of the 12th R.B. (Lieut.-Colonel MacLachlan) in the centre were surrounded, but fought their way back; and the 12th K.R.R.C. (Lieut.-Colonel Moore) on the left were heavily engaged with the enemy, who penetrated through Vaux and Fluquières. “A” Company of the 12th K.R.R.C. was practically cut off, but gallantly held on. In front of this company there was a gap in the wire through which the Germans tried to force their way four times, but two Lewis guns so successfully covered the gap that all efforts failed. Eventually, when all officers and many N.C.O.’s had been wounded or killed, the company was forced to fall back.
The pressure on the Corps front continued, and in view of the general situation the forward divisions were ordered to retire across the Somme during the night through the 59th and 60th Brigades, which after covering the withdrawal were to move back, fighting rearguard actions, to a position between Canizy and Béthencourt, and blow up all bridges on their front. At 8 P.M., before this movement was timed to take place, the enemy was reported to have broken through Vaux with a force of all arms, and the 20th Division was ordered to prolong the rearguard position held by the 59th Brigade to the right. The 60th Brigade accordingly occupied the line Bray—Douilly. Just before the troops moved back the Germans were heard advancing down a sunken road from Happencourt, singing for all they were worth. They had probably seen men of other divisions retiring and thought that the whole line had gone, and they were very much surprised and completely scattered when they suddenly came under Lewis gun fire from the 6th K.S.L.I.