When did Canada declare war on Germany in 1939?

Canada declared war on Nazi Germany on September 10, 1939, one week after Britain's September 3 declaration. Canada was the first British Dominion to declare war independently of Britain, exercising the sovereignty established by the Statute of Westminster of 1931. Prime Minister William Lyon Mackenzie King's federal Liberal government had recalled Parliament for a special session on September 7 to debate the question. Both the House of Commons and Senate passed the war motion on September 9, with formal royal approval from King George VI on September 10.

Mackenzie King's deliberate week-long delay served several purposes. It demonstrated Canadian constitutional independence, distinguishing Canada's decision from Britain's and from the almost-immediate declarations by Australia, New Zealand, and Britain (all on September 3) and South Africa (on September 6). It allowed Canadian Parliament to debate and approve the decision, satisfying the constitutional convention that war would be declared with parliamentary support. It also gave the Mackenzie King government time to negotiate purchases of American war materiel that would have been blocked by US neutrality laws if Canada had been at war before September 10.

The September 1939 debate was uncomfortable for the Liberal government. Mackenzie King had promised in his March 1939 statement that 'no Canadian Government would willingly send its manhood to fight in foreign quarrels' and had opposed extensive military spending throughout the late 1930s. By September 1939 the war had become unavoidable. Quebec Liberal Justice Minister Ernest Lapointe gave a key speech promising no conscription for overseas service, addressing French Canadian fears of a repeat of 1917. The English-Canadian Conservative leader Robert Manion supported the war declaration.

Canada's war effort grew massive over the next six years. About 1.1 million Canadians served in the Canadian Armed Forces (out of a total population of about 11.5 million in 1939), including about 1 million in uniform overseas. About 45,400 Canadians died and 55,000 were wounded. Canadian production grew 100 per cent during the war. The federal government spent about 22 billion dollars on the war (compared to 1939 federal expenditure of about 600 million dollars). The September 10, 1939 declaration marked the start of one of the most transformative six-year periods in Canadian history.