When the elected governor and clandestine secessionist Claiborne Fox Jackson and pro-secession legislators were driven from Jefferson City by a federal foray under Nathaniel Lyon, the state's renewed constitutional convention declared the governor’s seat vacant and on August 1, 1861, chose Hamilton R. Gamble as the state’s provisional governor. As a wartime governor, Gamble found himself and his government caught between pressures of loyalty and disloyalty, national and state authority, military and civil imperatives, and unionist factions in his home state.