- Main article: 1st Battalion in the Battle of the Lys (1918)
When the year 1918 opened the general situation on the Western Front had undergone some considerable change. The extent of ground held by the British had been increased by some 28 miles, and Sir Douglas Haig’s troops had now relieved the French on their right as far as the vicinity of the village of Barisis, immediately south of the river Oise, the relief being completed by the end of January. The defection of Russia permitted of the transfer of many German and Austrian divisions from the eastern to the Western Front, and it was increasingly evident at the end of 1917 and the opening of 1918, that the Western Powers must now adopt a defensive policy in view of the strong and sustained offensive which they might expect shortly to have to meet.
Towards the middle of February these signs of a big German offensive became more marked; it was known that the Central Powers had by this transferred 28 infantry divisions from the eastern and 6 from the Italian theatre; while not only were further reinforcements on their way to the West, but the enemy had also greatly increased his heavy artillery in that theatre of war, and by the end of the third week in March the number of German divisions here had risen to 192, an increase of 46 since the beginning of the previous November. Further air reconnaissances over the German lines showed that rail and road communications were being improved and that ammunition and supply dumps had increased in number along the whole front from Flanders to the Oise. By the end of February these preparations had become very marked opposite the front held by the Third and Fifth Armies, and General Haig came to the conclusion that the enemy would probably attack from the Sensée River southwards. The Third Army, it may here be stated, held a front of 27 miles from N. of Gouzeaucourt to S. of Gavrelle with the Vth, IVth, VIth and XVIIth Corps, while the front of the Fifth Army extended from our junction with the French just S. of Barisis to N. of Gouzeaucourt, a distance of about 42 miles, and was held by IIIrd, XVIIIth, XIXth and VIIth Corps.
For some little time past the heavy and increasing drain on the man power of the nation had been causing the military authorities very considerable anxiety, and it was finally reluctantly decided to carry out a reorganization of the divisional composition of the British Army in France; this measure was completed during the month of February, 1918, when the number of battalions in each brigade was reduced from four to three, and the number in a division from thirteen to ten.
“Apart from the reduction in fighting strength involved by this reorganization, the fighting efficiency of units was to some extent affected. An unfamiliar grouping of units was introduced thereby, necessitating new methods of tactical handling of the troops and the discarding of old methods to which subordinate commanders had been accustomed.” 
- Colonel H.C. Wylly, C.B. (1925). The Border Regiment in the Great War. Gale & Polden Ltd. ISBN 1847342728. p.171.
- Despatch dated 20th July 1918.