The United States and Canada today share the longest undefended border in the world, encompassing 5,525 after the U.S. purchased Alaska, and though they have long been allies, the border has not always been peaceful. During colonial times, generations of the British war with France meant generations of threats and of actual attacks by Canadian militia and allied Indians from New France. The British ended that threat from Canada by defeating France in 1763 and forever ending French rule in North America. When the 13 colonies rebelled against British rule, the Canadian colonies remained loyal, despite invitations from the American rebels and an invasion by American forces. When the Revolution ended, tens of thousands of Loyalists fled to Canada as refugees, strengthening loyalty to Britain. In the War of 1812, American forces again invaded Canada, and achieved several victories, but retreated in the face of British forces, a harsh climate and Canadian loyalty to Britain. Those were the last big invasions, but it took generations for the demilitarized border to become completely peaceful like it is today. Disenchanted Canadians, Canadian rebels and American sympathizers led incursions into Canada in the 1830s. The violence of the 1830s within Canada itself encouraged American groups to dabble, and Canadian radical reformers took refuge on the American side of the border as they plotted. Incursions over the border were strongly associated with attitudes regarding the British. Americans dedicated to democratic ideologies disliked the authoritarian way Canada was ruled and American Irish Catholics equated the social situation of Catholic French Canadians in Quebec with the conditions of Ireland under British rule. Confederates hoped to start a war between the Union and the British, to the benefit of the Confederacy. And American war planners anticipated a war with the British Empire, seeing Canada as a kind of hostage.
