Gas

"It reaches a point of suffocation to be subject to continual exertion with a gas mask on … it was pitiful to see the horses and mules affected by it."
The Germans were the first to use gas during the war, although the allies quickly retaliated in kind. The AIF experienced gas attacks in most actions on the Western Front. Gas bombardment of a wood at Messines led to 1,374 casualties, of which 310 were fatal.
Gas masks saved lives but also caused fatalities. They were extremely uncomfortable and hampered the movement of the men, inducing fatigue, disorientation, and confusion.
"It was terrible there were about four hundred men & they got out of hand & lost their heads … I daren’t keep my head cover on just held the mouth piece and nose clip, one cannot see as the glasses become misty & in the dark with shells falling and crashing all around you it is damned weird … it is the cruellest method of warfare of the lot."
Members of 2nd Australian Siege Battery wearing their gas respirators. E00693
Charles Blackman
"I don’t wish to go to back for a while yet. I am not well yet I might be going back to Hospital again. I am suffering from a very sore throat. I think its cause [sic] by gas when I was in Action at Ypres in Belgium."
Lance Corporal Charles Blackman, 9th Battalion, 15 June 1918
Charles Blackman was gassed while moving up to the jumping-off point for the battle of Messines Ridge on 20 September 1917. German gas shells landed among his company, but he quickly put on his gas mask and so was only lightly gassed and did not require hospitalisation. However, even a small dose of gas could affect soldiers’ health, and several months later Blackman was still feeling the effects.