|Battle of Loos|
The above picture is from the Battle of Loos, and that battle along with others in the fall, saw widespread use of gas. It did not take long to figure out proper countermeasures as well as where in the trench one should be when gas came. Counter-intuitively, the higher one was standing in a trench, the less likely one was to be affected by the gas. Being on the move helped too. Gas masks developed, even ones for dogs and horses, and the two sides started to develop mechanical means of overcoming the entrenched defenses.
It makes one wonder. For all the talk of how evil the Nazis were, why did they not gas the troop build ups in southern England? Why did they not gas the troops washing up on shore at D-Day? It seems odd they did not since the Allies prepared for gas attacks with clothing, Churchill planned to use gas if the Nazis ever landed in England, and we hear how the Nazis used gas in the Holocaust. Weird. One would think they'd have used all the tricks in their playbook to keep the D-Day invasions or even the Russian hordes at bay. Strange quirk of history.