Indian infantrymen are seen here training for gas attacks in a trench in France in 1915. There was about ninety thousand fatalities from a total of 1.3 million casualties caused by gas attacks in the war. Chemical weapons were used by all the countries who fought in the war. The use of gas constituted war crimes as its use violated the 1899 Hague Declaration concerning 'asphyxiating gases' and the 1907 Hague Convention on 'Land Warfare', which prohibited the use of 'poison or poisoned weapons' in warfare
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