Caroline affair
The Caroline Affair refers to a series of events beginning in 1837 that strained relations between the United States and Canada (and thus Great Britain). A band of Canadian rebels, led by William Lyon Mackenzie, seeking a more democratic Canada, took refuge on Navy Island on the Canadian side of the Niagara River, which separates the two counties (between Ontario and New York). American sympathizers supplied them with aid via the steamboat Caroline. On December 29, Canadian forces crossed to the United States and set the Caroline ablaze, sending the ship over Niagara Falls and killing one American in process.
In response on May 29, 1838 American forces burned British steamer Sir Robert Peel while it was in the United States. The tensions were ultimately settled by the Webster-Ashburton Treaty.
President Martin Van Buren sent General Winfield Scott to prevent further American incursions into Canada.