In the beginning of September 1812, Daniel Dobbins, a merchant on the Great Lakes, arrived in Washington, D.C. to warn the United States government of the vulnerability of the Lake Erie coastline to a British attack. Dobbins had been captured by the British after a surprise attack at Fort Mackinac in Michigan, but was able to negotiate his release. Dobbins was briefly detained again by the British in Detroit after the city was captured.