After mobile warfare had died down at the end of November 1914 a line a trenches stretched from the Belgian coast to the Swiss Alps. The BEF occupied a front of about 21 miles which at its most northern point was about 4½ miles south of the Belgian town of Ypres. The French Army occupied most of the remaining 350 miles of the Western Front and occupied the trenches to the north and south of the British. In December the Indian Corps (under British command) occupied an extra 4 miles to the south, and then in April 1915 the British took over a further 5 miles to the north. By the 17th April the transfer from the French to the British was complete. The British now held about 30 miles of the front and covered most of the salient around Ypres.

Map showing the initial attack at Ypres

The trench system that the British took over at Ypres was very shallow owing to water being only a foot or so below the surface. A more easily defensible line was the "G.H.Q" line which had been built by the French behind the front line. Its distance from the front varied from about 1½ to 3 miles and it consisted of redoubts four to five hundred yards apart, linked by trenches. In front of the "G.H.Q" line was a continuous belt of wire about six yards wide.

The Second Battle of Ypres is officially divided into 4 engagements. During the narrative, the term British is used to cover British, Canadian and Indian troops.

Battle of Gravenstafel Ridge (22nd - 23rd April)
At 5 p.m. on the 22nd April a heavy bombardment opened up on Ypres. At the same time the Germans released chlorine gas from cylinders in their front line trenches towards the north of the salient . The gas drifted slowly towards the French 45th and 87th divisions. Having no protection against the gas, they retreated in panic. This left a gap nearly 5 miles wide to the left of the Canadians. The German infantry advanced behind the gas cloud, but did not exploit the gap in the line to the full. Instead they preferred a strategy of securing limited objectives before advancing further. This allowed the British to bring up reinforcements to the threatened sector, but the gap was so large that it could only be thinly defended. 17½ British battalions were facing 42 German battalions with a superiority in artillery of five to one. Attacks on the 27th and 28th divisions' front prevented further reinforcements from being moved north. The British and Canadians counter-attacked on the evening of the 22nd and again on the 23rd, but achieved little.

Battle of St. Julien (24th - 4th May)
On the morning of the 24th April the Germans intensified their bombardment and again released chlorine gas but this time against the Canadians. It had been identified that the gas was water soluble chlorine, but in spite of only having the flimsiest of protection, such as wet handkerchiefs, the Canadians held their ground for several hours before being compelled to retire. During the following few days the British made several attempts to restore the line with mounting losses. On the 1st May, Sir John French (British Commander-in-Chief) ordered a general withdrawal of British forces in the salient. On the 2nd May the Germans attacked again with gas along a 3 mile front. This time the British shelled behind the gas cloud to catch the advancing infantry which helped to repulse the attack. By the 4th May the British withdrawal was complete.

Battle of Frezenberg Ridge (8th - 13th May)
During this phase of the battle of Ypres the Germans tried to smash through the front held by the 27th and 28th divisions by using their superiority in guns and ammunition. The front line trenches were obliterated, but despite this and the release of a further gas cloud on the 10th May they made little headway. By the end of the six day battle the Germans had advanced about a thousand yards.

Battle of Bellewaarde Ridge (24th - 25th May)
At about 3 a.m. on the 24th May the Germans released their largest gas attack yet across a 4½ mile front. Because of the favourable wind direction for the Germans, the British were alert to the danger and were able to repulse the initial attacks. However, as the day wore on the British were forced back in the north and south of the front. After unsuccessful counter-attacks the British withdrew a further thousand yards in the north to a more defensible line. The Ypres salient was now only 3 miles deep.

Devastation of Ypres, June 1915. (Photograph courtesy of the Imperial War Museum, London - Q52021)

Aftermath
Between the 22nd April and 31st May, the British suffered 59,275 casualties from the fighting at the Second Battle of Ypres and Hill 60 (just south of Ypres). The German losses are given as 34,933. Throughout the battle the Germans were able to use their superiority in artillery to continuously pound the defenders. Due to a shortage of shells, the British could only fire a daily average of about 3 shells per gun.

The battle marked the first use of poison gas in warfare for which the British were totally unprepared. Although initially there were no gas masks, by the end of April most of the troops had been issued with some sort of protection. However, it was not until September that the British were able to respond in kind when they attacked at Loos.