Everyone hoped it did not come to this
But, after the obvious failure of the Munich agreement, and Germany’s invasion of Poland, Britain declared war on Germany on September 3rd.
Unlike in WWI, this time Britain’s declaration did not automatically include Canada. Although there was never a doubt about Canada’s commitment, then Prime Minister Mackenzie-King wanted to assert Canadian independence on the issue and delayed for a week. On September 7, a special two-day session of the Canadian Parliament was called and gave approval for joining the war.
Canada mobilizes before Britain
The official declaration of war on Germany was made the following day, September 10.
What is little known is that even before Britain, Canada had begun a partial mobilization in August, and the Canadian Active Service Force was mobilized on September 1, two days before the British declaration of war, and well before its own declaration on September 10;
Canada was ill-prepared with a standing army of only about 4,500, and few dozen mostly outdated aircraft, and six destroyers.
A nation of only about 11 million at the time, soon had one million citizen volunteers in uniform. Many other Canadians had been signed into the British Royal Air Force or served with the British army and navy.
A mostly agricultural nation at the time, Canadian industry grew exponentially and turned almost exclusively to war manufacture.
Canada produced literally millions of machine-guns, pistols, and rifles, many millions more of ammunition and shells, along with artillery pieces, naval guns, warships, armed and unarmed cargo ships, bombers (eg Lancaster), trainers and fighters (eg Hurricane,Mosquito), tanks and armoured vehicles, communications equipment, uniforms, and hundreds of thousands of cargo and specialty military trucks as well as creating the largest air crew training programme in history.