Early in January 1918 orders were, however, received that in place of remaining assembled at one spot the Tank Corps was to form a defensive cordon stretching from about Roisel to a little south of Bethune—a frontage of some sixty miles. In February this line was taken up, tank units being distributed as follows:
| Fifth Army, 4th Tank Brigade | 1st Bn. Doingt wood. |
| „ „ H.Q. Templeux La Fosse | 4th Bn. Buire wood. |
| „ „ | 5th Bn. Buire wood. |
| Third Army, 2nd Tank Brigade | 2nd Bn. Velu wood. |
| „ „ H.Q. Thilloy | 8th Bn. Fremicourt. |
| „ „ | 10th Bn. Fremicourt. |
| „ „ 3rd Tank Brigade | 6th Bn. Wailly. |
| G.H.Q. Reserve, H.Q. Henincourt | 3rd Bn. Bray. |
| „ „ | 9th Bn. Bray. |
| „ „ 5th Tank Brigade | 13th Bn. Bray (unequipped). |
| „ „ H.Q. Bray. | |
| First Army, 1st Tank Brigade | 7th Bn. Boyeffles. |
| „ „ H.Q. Bois d’Olhain | 11th Bn. Bois des Alleux. |
| „ „ | 12th Bn. Bois de Verdrel. |
It will be seen that by this date the Tank Corps had grown from three to five brigades, in all thirteen battalions; machines, however, were short, and the total fighting strength in tanks at this time was only 320 Mark IV and 50 Medium A Tanks (Whippets) fit for action.
The general plan was that tank units should co-operate with Army and Corps reserves in the deliberate counter-attack against tactical points in what was known as the battle zone, a belt of ground running several miles in rear of and parallel to the forward or outpost zone; no retirement from this zone was to be contemplated. Prior to March 20 the weather had been fine, the ground was good and a thorough reconnaissance had been made of some 1,500 square miles of country; supply dumps had been formed and communication by wireless, cable, dispatch rider and runner established throughout the units of the Tank Corps.
On March 21 at 5 a.m. the German bombardment opened on a front roughly running from La Fère to the river Scarpe, with a break round the old Cambrai battlefield. The first tanks to be engaged were three forward sections of the 4th Battalion north-west of St. Emilie, north-west of Peizière, and at Geninwell copse. These came into action about noon and fought most gallantly against heavy odds. The first section, supported by two companies of the 2nd Royal Munster Fusiliers, recaptured a battery of guns near Esclairvillers wood; later on in the day this section assisted in the counter-attack of the Connaught Rangers on Ronssoy wood; meanwhile the second section cleared the bridge and cutting north-east of Peizière. Whilst these actions were being fought in the Fifth Army area, on the Third Army front one company of the 8th Tank Battalion co-operated with the 57th Infantry Brigade in a counter-attack on the village of Doignies. Zero hour was fixed at 6.40 p.m., but the attack was delayed and it was almost dark before the objective was reached. The village was cleared of the enemy, but on account of the darkness it was never completely occupied by our own men and eventually passed back into German hands.
On the following day, March 22, an Advanced Tank Corps Headquarters was opened at Hamencourt, a mile east of Doullens, in order to facilitate the battle liaison duties of the staff. On this day a most successful and gallant action was fought by the 2nd Tank Battalion in the neighbourhood of Vaux Vraucourt and Morchies. At 2.45 p.m. orders were issued for the 2nd Tank Battalion to advance and counter-attack the enemy, who had broken through the line Vaux Vraucourt-Morchies and was pushing forward towards Beugny. Two companies of infantry were detailed to support the tanks, but as eventually these could not be spared the tanks went into action alone. The counter-attack began to develop around Beugny at about 4.30 p.m. Concentrated artillery fire was brought to bear on the tanks, but in spite of this they advanced amongst the enemy, put a field battery out of action, and by enfilading several trenches full of Germans inflicted heavy casualties on them. The enemy was eventually driven back behind the Vaux Vraucourt-Morchies position, which was then reoccupied by our infantry. Thirty tanks took part in this action; seventeen of these were hit and 70 per cent. of casualties suffered by their crews. Heavy though these losses were the enemy had suffered severely, and more important still his plan of action was upset.
On the Fifth Army front the penetration effected by the enemy caused a rapid withdrawal of our troops, and to cover this the 4th and 5th Tank Battalions moved eastwards on either side of the Cologne river, which joins the Somme at Peronne; the village of Epehy was cleared of the enemy and much valuable time was gained at Roisel and Hervilly by tank counter-attacks. The German infantry would not face the tanks, and broke whenever they saw them advancing.
On March 23 no tank action was fought on the Third Army front. On the Fifth Army front, the 1st Tank Battalion, which had not yet been engaged, took up a position on the reverse slope west of Moislains with machine-gun posts pushed out on the forward slope. The enemy, however, would not attack the line of tanks but worked round their flanks—the 1st Tank Battalion eventually withdrew towards Maricourt. The 4th and 5th Tank Battalions covered the withdrawal of our infantry on either side of the Cologne river, and by the evening ten tanks of the 4th Battalion had concentrated at Cléry and those of the 5th Battalion at Brie bridge, three miles south of Peronne. Shortly after their arrival here this bridge was blown up and the whole of the 5th Battalion tanks, except three, had to be destroyed for lack of petrol. Of these three, one succeeded in crossing the bridge after the explosion and the remaining two effected their escape via Peronne. All three were lost on the next day.
The following day, the 8th Tank Battalion was engaged in a most successful action south-east of Bapaume. Two companies advanced against Bus and Barastre, while a third covered the 6th Infantry Brigade’s consolidation of a line of trenches. All tanks came into action and inflicted heavy casualties at close range, the enemy was checked for a considerable time and the 2nd Division was thus enabled to extricate itself from a most difficult position with little loss. The enemy was in force, but as was always the case, he would not face the tanks, and if he could not work round their flanks his advance halted until his guns could be brought up to deal with them.
It was on March 24 that a considerable number of Lewis-gun sections were first formed during this battle out of tank crews who had lost their machines. The 9th Tank Battalion handed its machines over to the 3rd Battalion and moved out as a Lewis-gun Battalion from Bray to assist the 35th Division and the 9th Cavalry Brigade in the defence of Montauban and Maricourt. The instructional staff of the Tank Driving School which, in February, had moved from Wailly to Aveluy, was rapidly formed into Lewis-gun sections, and with such tanks as were fit for action held a defensive line from Fricourt to Bazentin, covering the Albert-Bapaume road. The 5th Tank Battalion, south of the Somme, now without machines, was also formed into a Lewis-gun Battalion as crews were collected. This battalion in particular carried out most gallant and useful work, forty-five Lewis-gun groups being kept continuously in action. Several of these groups lost touch with their headquarters, but continued fighting with any troops in their vicinity until March 31.