Early in 1846, Larkin received instructions from Secretary of State James Buchanan to begin working covertly to assure all concerned that the United States would support any attempt at secession from Mexico. Toward this end, he secretly employed Abel Stearns to work in southern California. He volunteered to go to Mexico City on behalf of the United States to work out a peaceful settlement, but Congress had already declared war by the time his letter arrived in Washington. He had entered into a dialog with General Mariano Vallejo with the goal of arranging a peaceful annexation of California when the Bear Flag Revolt began on 14 June 1846 and the General was captured and imprisoned by a band of Americans who had heard a rumor that the Mexican authorities were thinking of arresting all Americans.