No state can get out of the Union on its own motion.
What kept the Army of the Potomac from marching into Richmond in the summer of 1862?
Walt
Secretary of War Stanton: "... the great ... aim of the war was to abolish slavery. To end the war before the nation was ready for that would be a failure. The war must be prolonged, and conducted so as to achieve that."
It seems there was a Confederate army in the way and a Secretary of War who wanted to prolong the war. There's two reasons for you.