At the outset of the
American Revolution, the
American revolutionaries regarded the presence of the
British Empire in the Canadian provinces as a strategic threat.
French Canadians were invited to join the resistance by sending representatives to the
Continental Congress, and Canada was pre-approved for joining the United States in the
Articles of Confederation. When
Canada was invaded during the
American Revolutionary War in an attempt to expel the British from
North America, Americans hoped French Canadians would join them in the effort. None of these measures proved successful in uniting Canada with the
thirteen American colonies as most Canadians sided against the U.S., although some Nova Scotians advocated joining the Americans. In peace negotiations,
Benjamin Franklin unsuccessfully attempted to convince British diplomats to cede Canada to the United States. The continued presence of the British Empire in Canada after the war helped to sour relations in the succeeding years, particularly since a great number of
Loyalist refugees from the American colonies resettled in Canada during and after the war.
The
Treaty of Paris (1783) which ended the war called for the British to vacate a number of fortifications along the
Great Lakes border. The British refused to do so, citing failure of the United States to provide financial restitution for Loyalists who had lost property in the war. The
Jay Treaty in 1795 with Great Britain resolved some lingering issues, but tensions mounted again after the turn of the century, erupting into the
War of 1812, when the Americans declared war on the British. The Americans were irked by British harassment of U.S. ships on the high seas, which was a by-product of British involvement in the ongoing
Napoleonic Wars. The Americans did not possess a navy capable of challenging the
Royal Navy, and so an invasion of Canada was proposed as the only feasible means of attacking the British Empire. Americans on the western frontier also hoped an invasion would bring an end to what they saw as British support of
American Indian resistance to the
westward expansion of the United States. The early strategy was to temporarily seize Canada as a means of forcing concessions from the British. As the war progressed, however, outright annexation was more frequently cited as a war aim. Many Americans hoped the Canadians would welcome the chance to overthrow their British rulers. However, the American invasion attempts were repeatedly repulsed, and the war ended as a bitter stalemate, with the animosity created lessening very gradually over the course of the 19th century as commercial and cultural ties grew.
Canada became a self-governing dominion in 1867 while retaining ties to the British crown. Strained relations with the United States continued, however, due to a series of armed incursions named the
Fenian raids by
Irish-American Civil War veterans across the border from 1866 to 1871 in an attempt to overthrow British interests in North America. While officially the American government did not openly endorse the raids, and did eventually move to disarm the Fenians, the raids created lasting anger in Canada. Many Canadians believed that
President Andrew Johnson initially supported the raids, and that the American government turned a blind eye to these armed incursions for far too long.
A
boundary dispute in the
Oregon Country (
Fifty-Four Forty or Fight!) was the most serious disturbance, but was peacefully resolved. In the 1930s, the United States studied plans to invade Canada in
War Plan Red, albeit as an academic exercise. Canadian defence was organized against an American invasion until the onset of
World War II.
Following co-operation in the two World Wars, Canada and the United States lost much of their previous animosity. As Britain's influence as a global superpower declined, Canada and the United States became extremely close partners. Canada was a close ally of the United States during the
Cold War.
The Canadian military has fought along side the U.S. in most major wars since World War II, including the
Korean War, the
Gulf War, the
Kosovo War, and most recently, the
war in Afghanistan. The main exceptions to this were the Canadian government's opposition to the
Vietnam War and the
Iraq War, which caused some brief diplomatic tensions. Despite these issues, military relations have remained close.