The Second Battle of Ypres 22 April - 25 May 1915

In the spring of 1915, the Allies retain the salient east of Ypres which was established in the First Battle of Ypres in October/November 1914. The Allied frontline in the Ypres Salient consists of a first line of shallow, relatively vulnerable trenches, supported by a stronger, second line ("GHQ Line") some three miles behind the first. The primary German offensive in the west during 1915 is aimed at eliminating the salient into their territory, loosening the Allied grip on Ypres, which commands the approach to the Channel ports. This offensive - the Second Battle of Ypres - is notable for its first use of poison gas on the Western Front. The German assault on Ypres begins on the evening of 22 April, with the release of chlorine gas against the 45th Algerian and 87th French Territorial Divisions' positions in the northern half of the salient, around Pilckem Ridge. The unprepared defenders pour backwards from their gas-filled frontline trenches, leaving a gap nearly five miles wide in the Allied line, only four miles in front of the city of Ypres. The Canadian Official History describes the effects of the Allies' first exposure to gas:

"The French troops surged wildly back over the (Ypres) Canal and through the village of Vlamertinghe just at dark. The Canadian reserves were amazed at the anguished faces of many of the French soldiers, twisted and distorted by pain, who were gasping for breath and vainly trying to gain relief by vomiting ...The chaos in the main streets of the village was such that any coherent movement of troops was, for the moment, impossible; gun-carriages and ammunition wagons were inextricably mixed, while galloping gun-teams without their guns were careering wildly in all directions. When order had been to some extent restored, Staff Officers learned from fugitives who were in a condition to speak that the Algerians had left thousand of their comrades dead and dying along the four-mile gap in our ally's line, through which the Germans were pouring behind their gas".

Second Ypres: An Experiment in Poison Gas, April-May 1915

Poison gas was still an experimental weapon when it was used in the German offensive against Ypres in the Spring of 1915. The Allies had not anticipated its use, and their quickly-improvised defences against it were primitive. As the gas used at Second Ypres was chlorine - a water-soluble gas - the primary protection for British (top left), Germans (right) and French (lower left) alike was a wet rag tied across the face. Gas warfare developed rapidly after its use at Ypres: phosgene gas was introduced in December 1915, mustard gas in 1917, and the method of delivery was improved when gas shells were developed to replace the unreliable tube dischargers used at Second Ypres. Despite the developments in technology - and the prominent place that poison gas occupies in the popular view of the Great War, due to the lingering death it inflicted on those affected by it - gas did not have a decisive military iimpact on the Western Front, as none of the belligerents ever found a way to advance safely and operate effectively through its own gas attacks, launched against enemy territory.

The twelve battalions of the Canadian Division, holding the sector of line adjacent to the French, are left exposed by the forced withdrawal of the French divisions, and hurriedly form a makeshift line of defence to protect their northern flank. On the evening of 22 April, and throughout the following day, the Canadians and nine battalions of the British V Corps launch a series of local counter-attacks towards Pilckem, despite being outnumbered two-to-one by the advancing German divisions. They take heavy losses, but by the evening of 23 April have plugged the gap in the line left by the French withdrawal. In the early hours of 24 April, the Germans renew their offensive with a new gas attack, this time against the Canadians. Having learned from the experience of the French, the Canadians are somewhat better prepared for the use of poison gas, and the CEF History records that:

"Although methods for resisting gas attacks were quickly developed when the need was realised, the Canadians were, of course, at this time unprovided with the proper means for witstanding them. They discovered that a wet handkerchief stuffed in the mouth gave relief. To fall back with the gas attack merely meant that one kept pace with it, while the effort of running, and the consequent heavy breathing, simply increased the poison in the lungs. The Canadians quickly realised that it was best to face the cloud, and hold on in the hope that the blindness would be temporary, and the cutting pain would pass away."

German Gains at the Second Battle of Ypres, April - May 1915

In desperate defence, the Canadians are pushed back as far as St Julien by the gas attack, but on the afternoon of the 24th they counter-attack, and eventually halt the renewed German assault. By the time the German attacks against St Julien end, on 30 April, the northern half of the salient has been flattened, leaving the British V Corps (in the southern half) vulnerable to attack on three sides. On 1 May, the British withdraw V Corps to a more easily defended frontline, approximating to their previous GHQ support line, a move which reduces the the Ypres Salient to a mere 2 � deep by 5 miles across. The Allied troops crowded into the reduced salient are a target for heavy artillery and gas attacks through May 1915 but, as they now hold a better fortified defensive line, they are able to prevent significant German gains. By 25 May, German supplies of shells are exhausted, and they abandon their attempt to eliminate the Salient. The Second Battle of Ypres, which has cost the Allies 70,000 casualties and the Germans probably 30,000, is over.

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