Soon after taking office, President Martin Van Buren faced a diplomatic crisis with Great Britain. It grew out of tensions between Americans, Canadians, and British soldiers along the borders between New York and Canada and Maine and Canada.

Problems began when a small separatist movement in Canada sought to gain independence from Britain in late 1837. After an unsuccessful uprising, these dissidents retreated to the United States, recruited a number of American citizens to their cause, and took refuge on an island in the Niagara River, which divides the United States—and specifically New York—from Canada. Some Americans began selling guns and supplies to the Canadian separatists. In response, the British ordered loyalist Canadian forces to attack the ship being used to supply the rebels. The loyalist Canadians boarded the Caroline, set it ablaze, and pushed it over Niagara Falls, killing one American. Considerable sentiment arose within the United States to declare war on England, and a British ship was burned in revenge.

Van Buren looked to avoid a major diplomatic row with Great Britain and he rejected the possibility of an aggressive response. Instead, he sent General Winfield Scott to the region to impress upon American citizens the need for a peaceful resolution to the crisis, and to make it clear that the U.S. government would not countenance adventuresome Americans attacking the British. Also, in early January 1838, Van Buren proclaimed U.S. neutrality with regard to the Canadian independence issue, a declaration which Congress endorsed by passing a neutrality law designed to discourage the participation of American citizens in foreign conflicts. Each of these actions had the effect of calming the situation.

A new crisis surfaced in late 1838,however, along the border between Maine and Canada, where Americans began settling on lands claimed by both the United States and Great Britain. When British troops forcibly removed some of the settlers and imprisoned others, tensions between British officials and the governor of Maine, John Fairfield, rose to a fever pitch. Fairfield even called on Van Buren to send troops to the area.

To settle the Maine crisis, Van Buren met with the British minister to the United States. They agreed to resolve the border issue diplomatically. Van Buren also sent General Scott to Maine with orders to rein in Governor Fairfield and others who were exacerbating the tensions. Again, Van Buren's tactics worked. The diplomatic negotiations begun by Van Buren resulted, in 1842, with the signing of the Webster-Ashburton Treaty between Great Britain and the United States that resolved these border issues.

Van Buren's patient diplomacy, which defused tensions between the United States and Great Britain, kept America out of war. But his pursuit of negotiations and accommodation in the face of the loss of American property and lives only angered those in Maine and New York who wanted him to take a tougher stance. The criticism Van Buren took in both cases was quite considerable, and added to the substantial indictment his opponents filed against his presidency.