The first indication of the break-through which the Battalion received was enemy bullets actually falling in the camp. Every man turned out, the Battalion took up a line north of Equancourt in an attempt to hold up the advance of the enemy, patrols being sent forward into Fins, where it was found the Germans had succeeded in establishing themselves.
On the following morning an enemy attack was beaten back with heavy loss, but both its flanks being "in the air" the Battalion received orders to retire on Le Transloy. Moving though Hayettes Wood, Ytres, Bus, and Rocquigny, Le Transloy was reached late at night, where the Brigade from which it had become separated was rejoined.
Moving again before dawn, a line was taken up round Gueudecourt, which was held during the day. Making another move at dusk, a fresh line was established at Eaucourt l'Abbaye. Very heavily attacked on the following day, the Battalion was forced to fight a rearguard action, retreating through Le Sars on Pys, where another stand was made.
Again slipping back at night, a position was taken up near Beaucourt sur Ancre. From this position the Battalion again moved back and occupied the old British trenches known as White City trenches near Beaumont Hamel. In spite of many heavy enemy attacks this position was held until the Battalion was relieved by New Zealand troops.
On relief it marched out to the wood at Mailly-Maillet only four officers and seventy men strong.
Resting at Englebelmer for a day or so, it was again moved into the front line at Aveluy Wood, where a German attack was beaten off, the enemy being badly mauled. During the fighting round Gueudecourt, Brigadier-General Barnett-Barker was killed, and, as senior Colonel in the 99th Brigade, Lieutenant-Colonel Winter assumed command, the command of the 23rd Royal Fusiliers devolving upon Major Lewis.
In his anxiety to hold up the enemy for as long as possible and to get the battalion back safely to a line being formed behind him, Major Lewis was taken prisoner at Eaucourt l'Abbaye. The command then devolved upon Captain C.H. Bowyer, who kept it until the return of Lieutenant-Colonel Winter, who rejoined the Battalion on General E. Ironside (now General Sir E. Ironside, who earned fame in Russia) taking over the Brigade.
It only remains to add that the gas casualties from March 12 onwards amounted to 11 officers and 240 other ranks, while the casualties in action from the 22nd to the 31st were:
| Officers killed | 1 |
| Officers wounded | 2 |
| Officers wounded and missing | 1 |
| Officers missing | 10 |
| Other ranks killed | 15 |
| Other ranks wounded | 59 |
| Other ranks wounded and missing | 6 |
| Other ranks missing | 210 |
During the early part of April the Battalion was busy in moving, being in turn in Hedeauville, Beauval, Houvin, Houvigneul, Ivergny, Coullemont, La Cauchie, and on the 14th relieved the 1st Coldstream Guards in Brigade Reserve in front of Blaireville. Two days later it was in the front line, right sub-sector, in front of Adinfer, doing alternate front line and support duty until the end of the month.