The Second Battle of Ypres: Chlorine Gas and the Fight to Hold the Salient

On the evening of 22 April 1915, at around 5pm, sentries on the Allied front line north of Ypres noticed a yellowish-green cloud moving towards them from the German positions near Langemarck. They had no frame of reference for what they were seeing. Chemical weapons of this scale had never been used in warfare.

The cloud was chlorine gas. 168 tonnes of it, released from approximately 5,730 cylinders along a 6.5km front.

What followed, the collapse of the French and Algerian divisions hit by the gas, the gap torn in the Allied line, and the desperate effort to hold Ypres in the days that followed, was the Second Battle of Ypres.

The gas attack: what happened

The chlorine cloud drifted on the prevailing wind towards the French 45th (Algerian) Division and the French 87th Territorial Division on the left of the Allied line. Neither had gas masks. Neither had any preparation for what was coming.

The gas caused immediate casualties and complete disorganisation. A gap approximately 6km wide opened in the Allied line. For a brief period on the evening of 22 April 1915, there was virtually nothing between the German advance and Ypres itself.

The Germans did not fully exploit the gap, partly because their own commanders were uncertain about advancing through the contaminated ground, partly because the scale of the breakthrough had not been anticipated in their planning. By the time German infantry moved forward, Canadian forces to the right of the breach, the 1st Canadian Division under General Alderson, had begun to respond.

The Canadians improvised. With no gas masks, men were told to urinate on cloths and hold them over their faces, ammonia in urine has some neutralising effect on chlorine. They held the flank. The gap was partially closed overnight. Ypres did not fall.

The Canadian role

The 1st Canadian Division's response on the night of 22-23 April 1915 is one of the most significant episodes in Canadian military history. Their decision to counter-attack rather than retreat stabilised the line at a critical moment.

The Canadian counter-attack at Kitcheners Wood on the night of 22-23 April, two battalions advancing in the dark without artillery support to recapture a wood from the German forces advancing through the gap, was a costly action that achieved its tactical aim. It is the kind of episode that military historians study and that most Canadians have never heard of.

The Second Battle of Ypres established the Canadian Corps' reputation for tenacity under pressure that it maintained for the rest of the war.

The German cemetery at Langemarck

The German Cemetery at Langemarck, 5km north of Ypres, sits near the position from which the gas was released on 22 April 1915. It is one of the most distinctive sites in the Salient, the grey basalt lava headstones (flat crosses and low tablets, not the white Commonwealth upright markers) and the oak trees make it visually completely different from the CWGC cemeteries.

44,294 German soldiers are buried at Langemarck, more than any other German cemetery in Belgium. A mass grave at the back contains the remains of 24,917 soldiers, buried together because individual identification was not possible.

The Kameraden Grab, the Comrades' Grave, and the four bronze figures standing watch over it are among the most powerful memorial images on the entire Western Front.