I found this, I am just surprised the soldier had a Canadian stamp on him and I doubt that he needed it- see where he wrote (Canada)
Why did Canada join ww1?
The Canadian Parliament didn't choose to go to war in 1914. ... So when Britain's ultimatum to Germany to withdraw its army from Belgium expired on 4 August 1914, the British Empire, including Canada, was at war, allied with Serbia, Russia, and France against the German and Austro-Hungarian empires.Aug 5, 2013
First World War (WWI) | The Canadian Encyclopedia
https://www.thecanadianencyclopedia...orld-war-wwi