In Missouri, an elected convention on secession voted to remain in the Union. When pro-Confederate Governor Claiborne Fox Jackson called out the state militia, it was attacked by federal forces under General Nathaniel Lyon, who chased the governor and rest of the State Guard to the southwestern corner of Missouri (see Missouri secession). Early in the war the Confederacy controlled southern Missouri through the Confederate government of Missouri but was driven out after 1862. In the resulting vacuum, the convention on secession reconvened and took power as the Unionist provisional government of Missouri.