In 1837 the internal Lower and Upper Canada Rebellions were defeated by British forces.
In 1865 an Irish gang the Fenian Brotherhood arose on the border with the USA, but the USA worked just as hard to control them as Canadians did. However, there was a real invasion threat then, of USA expansion up the west coast. It was defeated, not by arms but by the brilliance of John A. Macdonald, who espoused and worked out how to build the transcontinental railway from both ends at the same time, thus actively involving British Columbia in joining Confederation to dissuade them from joining the USA.
In 1885, 5,000 Canadian militia were sent to Saskatchewan to crush the North-West Rebellion.
Ever since, apart from a police-level skirmish at Oka, Canadians have fought other nation's wars.
Until 1931, the Statue of Westminster, Canada was considered a colony of Great Britain, so automatically took part in British wars:
• In 1884, Canada fought the Mahdi of Sudan along with British forces.
• In 1899, Canadian forces joined those of Great Britain to defeat Boer independence in South Africa.
• In 1914, Great Britain declared war on Germany, thus involving Canada. Although called a world war by some, it was in fact solely a European conflict.
• In 1919, Canada joined British troops in Siberia to aid the White Russians in the Russian Civil War.
After 1931, as an independent nation:
• From 1937 until at least 1970 Canada produced chemical and biological weapons in large quantities and tested them on over 2000 Canadian soldiers for Britain and the USA.
• In 1939, Canada declared war on Germany out of loyalty to Great Britain, although no longer required to, and defended British interests in Europe.
• In 1941 we declared war on Japan, again in concert with Great Britain, after Japan's attack on Hong Kong.
• From 1948 to 1991, as a member of the UN, Canada sent armed "peace keeping" missions to Kashmir, Cyprus, the Sinai and Golan Heights, Bosnia, and Somalia.
• In 1949, Canada joined NATO thus actively involving ourselves in unifying Europe and fighting the expansion of Russian influence there.
• In 1950, we joined with NATO to divide Korea.
• In 1957 we joined with the USA to form NORAD, the (joint) North American Aerospace Defense Command.
• In 1990 an internal revolt by Mohawk at Oka was suppressed by Canadian militia.
• In 1991 we defended Kuwait against Iraq as part of a UN operation (Gulf War).
• In 2001 we took sides in a conflict in Afghanistan to support the USA.
150 years after Confederation, there is still no external threat to Canadian territory. We still maintain armed forces, but only spend 1% of our GDP on them.