On this day in history, Germans fired more than 150 tons (168 long tons) of lethal chlorine gas over the four mile front against two French colonial divisions (Moroccan and Algerian troops) at Ypres in Belgium, during the so-called Second Battle of Ypres. Poison gas had been used before at the Battle of Bolimov three months earlier but the gas liquified in the cold and became inert.
The German troops carried 5,730 gas cylinders, weighing 90 pounds each, to the front by hand. They relied on the prevailing winds to carry the gas towards enemy lines, which inevitably resulted in a large number of German casualties as well.
The French troops in the path of the gas cloud had some 6,000 casualties, many of whom died within ten minutes. The chlorine gas, being denser than air, quickly filled the trenches, forcing the troops to climb out into heavy enemy fire.
Apparently, captured German soldiers had previously revealed the imminent use of gas on the Western Front, but their warnings were not heeded.
The Allies were outraged, but the Germans retorted that the French had been manufacturing and employing the gas in battle well before Ypres. (The French did employ gas first during World War I, in August 1914. They used tear-gas grenades containing xylyl bromide to meet the initial German advance in Belgium and northeastern France.) The gases employed by the Germans, however, were much deadlier, and included chlorine gas, phosphene gas, and mustard gas. Britain and France also began to use these in response to their use by Germany.
The British were the first to respond, with “Special Gas Companies.” The men who served in these companies weren’t allowed to refer to the word “gas” in their operations, however. Instead they had to call their gas canisters”accessories”; use of the word “gas” brought with it a threatened punishment.
The Allied forces who used gas had the same problems as did the Germans; the air currents were fickle, and could turn the attack on their own men. It became apparent that a more reliable delivery mechanism was needed, and experiments began with gas-filled artillery shells and other devices. By 1918 the use of poison gases had become widespread, particularly on the Western Front. If the war had continued into 1919 both sides had planned on inserting poison gases into 30%-50% of manufactured shells.
In total, while there were some 1.25 million casualties from gas used in the were, there were only about 91,000 deaths from gas poisoning, with over 50 percent of those fatalities suffered by the poorly equipped Russian army.
After the Armistice, the wartime use of poison gases was outlawed in 1925 – a ban that is, at least in theory, still in force today. Even at that time, the Germans continued to work on developing poisonous gas, and in the early 1920s invented Zyklon B, a cyanide-based pesticide used by Nazi Germany during the Holocaust to murder physically and intellectually disabled people, political undesirables, and Jews. It was pumped into locked gas chambers after they were filled with victims.