On 4th May 1914, the Battle of St Julien ended after 11 days. It was one of the key engagements during the Second Battle of Ypres.
According to Wikipedia, the Battle of St. Julien was “the first time a former colonial force (the 1st Canadian Division) defeated that of a European power (the German Empire) on European soil”.
The Second Battle of Ypres was the main conflict on the Western Front between April and September 1915. The battle was for control of the town of Ypres in western Belgium. If the Germans broke through here, they could have had access to the Belgian ports.
The Second Battle of Ypres marked the first mass use by Germany of poison gas on the Western Front – read more here.
According to Wikipedia, the Second Ypres conflict had six engagements:
The Battle of Gravenstafel: 22 April – 23 April
The Battle of St. Julien: 24 April – 4 May
The Battle of Frezenberg: 8–13 May
The Battle of Bellewaarde: 24–25 May
The Battle of Hooge: 30–31 July
The Second Attack on Bellewaarde: 25 September.