The Battle of Ypres was a series of battles during World War I near the Belgian city of Ypres, between the German and Allied forces (Belgian, French, and British). The battles resulted in over one million casualties across five major engagements:
First Battle of Ypres (19 October – 22 November 1914): Over 220,000 casualties.
Second Battle of Ypres (22 April – 15 May 1915): First large-scale use of poison gas by Germany; about 100,000 casualties.
Battle of Passchendaele (31 July – 10 November 1917), also known as the Third Battle of Ypres.
Third Battle of Ypres: Between 400,000 and 900,000 casualties.
Battle of the Lys (7 – 29 April 1918), also called the
Fourth Battle of Ypres: Around 200,000 casualties.
Fifth Battle of Ypres (29 September – 2 October 1918), also known as the
Advance of Flanders: Approximately 10,000 Allied casualties; German casualties unknown.