article: Second Battle of Ypres
links: Hague Convention Gas mask France World War I Belgium Battle of Hill 60 (Western Front) Western Front (World War I) Salients, re-entrants and pockets British India French Third Republic United Kingdom of Great Britain and Ireland Algeria German Empire Ypres Canadians Surveillance Casualty (person) Chlorine gas Withdrawal (military) Military intelligence Russia Allies of World War I