Third, the southerners saw an invading army coming from Washington City to tell them how to live their lives. That is what caused VA, NC, TN, and AR to leave the Union - Lincolns call for troops to invade their neighbors who just wanted to withdraw from the Union. SC, FL, GA, and the other 4 states of the original seven Confederate states didn't send troops to invade OH or PA or IL, in April, 1861 did they? Nope, they said that they were not part of the club anymore, thank you very much.
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I see this as the short come of the Southern leadership. Had they gone on the offensive and taken Maryland, marched on PA and threatened Philly, or Trenton NJ the North would have thrown up it's arms and allowed the South to leave, probably taking MD with it. But as long as the war was somewhere else the North was not under political pressure to end the war and stop the South from assaulting the people of (pick a boarder state) maryland, Delaware, Pennsylvania, New Jersey, New York.
As long as the war was not fought on Union territory, the only steak the North had in the fight was the young men. With millions of men in Uniform, Needing leather goods, uniforms, arms, munitions, food the northern industries were booming feeding the war machine. Money was to be made, glory was to be earned by comanders in saving the Union.