Canada may have gained its independence from Great Britain in 1867, but was it truly a sovereign country right after confederation? Many people believe that Canada was its own "strong and free" nation since 1867, but how could it be when it didn't even have its own constitution at the time? On a map, Canada appeared to be an independent nation, when in reality, it was still very dependant on Great Britain. The Canadian Flag still consisted of the Union Jack, Canadians still sang "God Save the Queen", and the British always had the final say, when it came to making laws.
As soon as Britain declared war on Germany on 1914, Canada was forced into the war as well because of its strong ties with Great Britain. Canada could not really refuse because of how close the newly formed nation was to the United Kingdom, so it joined in the conflict. Countless Canadians were killed in the war that lasted five years, but in the end, the allied forces were successful in defeating Germans. This proves that Canada had to follow whatever the British did at the time, and was still a British puppet.
During the Second World War however, Canada did not join the conflict until one week after the British declared war on Germany. They remained neutral for the first week, because they did not really know the severity and complexity of the war, and didn't want to join the war just because the British were fighting in it. They wanted to make their own decision, and in the end, they decided to fight alongside Great Britain during the war. This proved that Canada could make its own decisions by then, and did not have to listen to absolutely everything that the British said.
In the late nineteenth and early twentieth century, if something was to be changed in the constitution, it had to be passed through the Canadian Parliament as well as its British counterpart before it could come into effect. This changed when the Statute of Westminster was signed on 1930, so that changes in the constitution did not have to pass through the British Parliament anymore, but the document still remained in Britain.