Query: On which date did Tennessee enter a military alliance with the Confederacy?
Context: Following the Confederate attack upon Fort Sumter in April and Lincoln's call for troops from Tennessee and other states in response, Governor Isham Harris began military mobilization, submitted an ordinance of secession to the General Assembly, and made direct overtures to the Confederate government. The Tennessee legislature ratified an agreement to enter a military league with the Confederate States on May 7, 1861. On June 8, 1861, with people in Middle Tennessee having significantly changed their position, voters approved a second referendum calling for secession, becoming the last state to do so.