1915-4-22 Chlorine gas, 2nd Battle of Ypres

.22nd April 1915: Chlorine gas marks the start of the Second Battle of Ypres > .

On 22 April 1915 poison gas was first used effectively in the First World War at the Second Battle of Ypres.

A form of tear gas had previously been used by the Germans fighting the Russians at the Battle of Bolimów in Poland at the end of January, but it had proved wholly unsuccessful. The freezing temperatures meant that a lot of the gas failed to vaporise, and that which was successfully released was blown back towards the German trenches due to a change in the direction of the wind.

At Ypres, near the small Belgian hamlet of Gravenstafel, the situation was dramatically different. 5,700 gas canisters weighing over 40kg each were released by hand over a 4 mile (6.5km) stretch of the front line. Every canister contained highly poisonous chlorine gas. Despite the improved organising, the rudimentary system of release still depended on the wind to blow the gas towards the enemy. Some Germans were killed or injured in the process of releasing the gas but the attack was terribly effective as the gas successfully vaporised and sank into the enemy trenches.

Over five thousand French Algerian, Moroccan and territorial troops died within ten minutes of the gas being released. A further five thousand were temporarily blinded, with nearly half of them becoming prisoners of war.

The Germans didn’t expect the gas to be as effective as it was, and so didn’t fully exploit their initial advantage. However, by the end of the battle on 25 May, the Germans had certainly scored a tactical victory. They had compressed the size of the Ypres salient and had demonstrated the effectiveness of chemical warfare. The Allies soon developed their own poison gas, making chemical warfare part of the offensive strategy for the rest of the war.