The Caroline affair was a diplomatic crisis beginning in 1837 between the USA, Britain, and Canada. It began during the Rebellion of 1837 when William Lyon Mackenzie and other Canadian rebels commanding the ship Caroline fled to an island in the Niagara river with support from nearby Americans. British forces then boarded the ship, killed an American crew member, burned the ship, and sent it over Niagara Falls. The incident outraged the American government and, in retaliation, a group of American and Canadian raiders attacked and destroyed a British ship. There were several other attacks in 1838 between the British and Americans in an undeclared mini-war, but the situation was finally resolved by the Webster-Ashburton Treaty in 1842 in which both the Americans and British admitted to wrongdoing. In the aftermath, the incident led to the legal principle of the Caroline test, which states that the necessity for self-defense must be "instant, overwhelming, and leaving no choice of means, and no moment for deliberation" as stated by Daniel Webster in his response to British claims that they attacked the Caroline in self-defense. The Caroline affair, which seems somewhat ridiculous when looked through a modern lens, at least led to a principle of international diplomacy that still applies today in the use of force.