On this day, 22 April at 5 p.m. CET the first major chemical attack in modern warfare began 98 years ago, when German Imperial Forces released between 150–168 tonnes of chlorine gas from almost 6000 cylinders along a 700-metre front near the Belgian town of Ieper.
In a study for SIPRI published in 1997, I summarised the opening of the 2nd Battle of Ypres as follows:
Modern chemical warfare is regarded as having begun on 22 April 1915. On that date German troops opened approximately 6000 cylinders along a 7-km line opposite the French position and released 150–168 tonnes (t) of chlorine gas. Tear-gas (T) shells were also fired into the cloud and at the northern flank, the boundary between French and Belgian troops. Between 24 April and 24 May Germany launched eight more chlorine attacks. However, chemical warfare had not been assimilated into military doctrine, and German troops failed to exploit their strategic surprise. Chemical weapon (CW) attacks in following weeks were fundamentally different as they supported local offensives and thus served tactical purposes. In each case the amount of gas released was much smaller than that employed on 22 April, and crude individual protection against gas enabled Allied soldiers to hold the lines.
Prior to the April 1915 use of a chlorine cloud, gas shells filled with T-stoff (xylyl bromide or benzyl bromide) or a mixture of T-stoff and B-stoff (bromoacetone) had been employed. In addition, as early as 14 February 1915 (i.e., approximately the same period as CW trials on the Eastern front) two soldiers of the Belgian 6th Division had reported ill after a T-shell attack. In March 1915 French troops at Nieuwpoort were shelled with a mixture of T- and B-stoff (T-stoff alone had proved unsatisfactory). In response to the British capture of Hill 60 (approximately 5 km south-east of Ypres), German artillery counter-attacked with T-shells on 18 April and the following days. In the hours before the chlorine attack on 22 April the 45th Algerian Division experienced heavy shelling with high explosive (HE) and T-stoff.
Such attacks continued throughout the Second Battle of Ypres. Although Germany overestimated the impact of T-shells, on 24 April their persistent nature appears to have been exploited for the first time for tactical purposes. Near Lizerne (approximately 10 km north of Ypres) German troops fired 1200 rounds in a wall of gas (gaswand) behind Belgian lines to prevent reinforcements from reaching the front. The park of Boezinge Castle, where Allied troops were concentrated, was attacked in a similar manner.
Just a small thought that almost a century later we are still worrying about the possibility of the use of gas in war.