Which event is primarily associated with the official start of World War I for Canada?

The event that signifies the official start of World War I for Canada is the declaration of war against Germany. Canada entered the war automatically when Britain declared war on Germany on August 4, 1914, because Canada was a dominion of the British Empire at the time. The declaration marked Canada's commitment to the war effort, mobilizing resources and troops to support the Allies. It was a pivotal moment in Canadian history, as it marked the nation's involvement in a global conflict and fostered a sense of national identity, distinct from Britain. The other events mentioned, while significant in their own contexts, do not represent Canada's official entry into the war as directly as the declaration did.