In the wake of Germany's invasion of Poland, Britain declared war on Germany on September 3, 1939. Canada, a Dominion of the British Empire, was faced with the decision to follow suit. On September 10, 1939, at 11:00 a.m. EST, the Canadian Parliament convened for an emergency session. Prime Minister William Lyon Mackenzie King presented a resolution to declare war, which received royal assent shortly thereafter, signifying Canada’s official entry into World War II. The act was a momentous step, as it was taken without prior consultation with Britain and demonstrated Canada’s burgeoning autonomy on the global stage.

The declaration was met with mixed emotions across the nation. Many Canadians supported the war effort, motivated by a sense of duty to protect democracy and freedom. Conversely, there were significant anti-war sentiments, particularly among isolationists who had witnessed the devastation of World War I. Military recruitment drives began almost immediately, as both the government and citizens prepared for a prolonged conflict.

Canada's declaration of war not only marked its participation in WWII but also highlighted its evolving national identity. As the conflict unfolded, Canada would eventually evolve into a key player on the world stage with contributions that included the creation of the British Commonwealth Air Training Plan and extensive involvement in several pivotal battles.