The gas cloud and artillery bombardment were followed by raiding parties, which made temporary lodgements in the British lines.

A large number of German casualties were caused by the change in the wind direction and the decision to go ahead despite protests by local officers.

In early 1916 the British took over more of the Western Front, to allow the French Tenth Army to move south to Verdun, ground which was just as tactically disadvantageous.

The possibility of a withdrawal to more easily defensible ground was rejected by Joffre, the French Generalissimo and all the Allied commanders preferred to improve their positions by advancing.

With this in mind, the French and British made far less effort to improve their defences, which conceded another advantage to the Germans, who could attack positions protected by far less extensive barbed wire barriers and few deep-mined dugouts than their own.

[1] In early 1916, the Germans had more and better equipment for trench warfare, with good quality hand grenades, rifle grenades and trench mortars; the Germans made more effort to repair and improve defences and with a homogeneous army, found it easier to move artillery, ammunition and men along the front.

Four reserve artillery batteries were moved into the 15th (Scottish) Division area and all units were required to rehearse gas alerts daily.

After thirty minutes, groups of German infantry about 20–30 strong, equipped with pistols and hand grenades, were seen heading for gaps in the British wire and were repulsed by rifle and machine-gun fire.

[11][b] Behind the second gas cloud, larger parties of German infantry advanced and managed to get into the British trenches for brief periods at three points.

At Chalk Pit Wood the British had a howitzer, which had been brought up in September 1915, to fire in support of an attack on Hulluch.

Since the Lone How was only 40 yd (37 m) behind the British front line, orders had been given to destroy it, in the event of a German raid and a demolition charge had been left on the gun with a lit fuze.

At 3:45 a.m., a German artillery bombardment and gas discharge began on the 16th (Irish) Division front but the expected attack did not occur.

The troops most affected by the gas could not be relieved immediately but were exempted from carrying duties for the next day and no ill effects were reported.

British troops were said to have been greatly encouraged by the German fiasco but uneasy about the protection offered by their PH gas helmets.

[10][d] German casualties in BIR 5, BRIR 5, PR 36 who operated the gas cylinders and other non-infantry troops were not known in 1932, when the British Official History was published.