"Dusk was falling when from the German trenches in front of the French line rose that strange green cloud of death. The light north-easterly breeze wafted it toward them, and in a moment death had them by the throat. One cannot blame them that they broke and fled."
(Capt. A.O. Pollard, “Fire-Eater: the Memoirs of a VC”)
In the spring of 1915, the German general staff was focused on the operations that were being developed on the eastern front and limited themselves to remaining on the defensive on the one in the west. Despite this, General von Falkenhayn decided to launch a limited offensive operation in the area of Yprés, in Belgium. After a fierce battle in the same area between October and November of 1914 (First battle of Yprés or Battle of Flanders), the Allied forces managed to create a salient, i.e. a kind of wedge, between the enemy lines, approximately 7 kilometres deep. The elevated position of this salient made the German operations difficult, which had the city of Yprés within its sights and, for this reason, it was decided to attempt to take it.
The operations began on 22 April, when the German IV° army, commanded by Duke Albert von Württemberg, released approximately 168 tons of sulphur dichloride along the line of the front, taking advantage of the wind for it to reach the enemy lines. The unexpected chemical attack caused 6,000 deaths in less than ten minutes among the French and Algerian troops, leaving open a front of approximately 7 kilometres.
The Germans themselves did not expect such a result and delayed the advance, allowing the British II° army of General Horace Smith-Dorrien to fill the gaps. During the second wave of the German attack, from 24 April to 4 May, Smith-Dorrien asked French permission to retreat from the salient to a more defensible position, but this was refused. This led to his replacement by Herbert Plumer and to a French counteroffensive that failed, after very high losses, costing the loss of a part of the salient.
On 8 May the Germans managed to seize of the crest of Frezenberg. To defend it there were the Canadian soldiers of the Princess Patricia light infantry battalion. Fearing a gas attack, the Canadians adopted rudimentary measures to prevent it. In practice, they used handkerchiefs and gauze soaked in urine to protect the mouth and the nose, given the ability of uric acid to neutralize the effects of the mustard gas. Despite the precautions and the extreme courage demonstrated in the counterattack, the Canadians lost two thirds of their contingent and all the officers except two lieutenants. With the last attack near Bellewaarde, between May 24 and 25, the Germans definitively took control of the salient and were able to occupy an elevated position only three kilometres from Yprés which then became the objective of German artillery.
The Second battle of Yprés, fought for a strip of land, became significant for many reasons. It was the first theatre of battle, from the beginning of the conflict, involving a massive and effective use of chemical weapons. Gas was not a novelty and its use had been known from before the war. However, was it was not considered civilized and it was very probably trench warfare that pushed armies toward its use. The Germans used them for the first time at Neuve Chapelle, in October of 1914, but to such an extent that the French were caught unawares. A later attempted chemical attack in January of 1915 at Bolinov, on the eastern front, failed because of the low temperatures that prevented the evaporation of the gas. For these reasons, the efficiency of the gas at Yprés was not foreseen by the Germans themselves, who did not manage to benefit fully from the advantage. The battle also shed light on the limits of the use of the gas, connected to the environmental and meteorological conditions and the morale of the soldiers who often, even with the masks, refused to go occupy the positions freed from the enemy. For this reason, starting from 1916, artillery projectiles were designed that could launch gas at a long distance. Countermeasures followed the development of the gas, making chemical warfare increasingly less effective in terms of ending human life, while maintaining a high psychological impact.
The battle of Yprés shed light on the inadequacy of the tactics and training on both sides. The Germans could not break through despite the toll of the gas. The Allied troops were unprepared for chemical attack and undertook impressive losses in a futile counteroffensive from positions of disadvantage. Finally, in Yprés, the Canadians troops had their baptism by fire when, intended to be behind the front lines, they gained promotion to the front with very high losses, in a battle that became one of the symbols of their national emancipation.