But there were flaws in the Union sword and hidden strengths in the Confederate shield. Northern success paradoxically created military weakness. Union armies had to detach many divisions as occupation forces to police 100,000 square miles of conquered territory. Other divisions had similar responsibilities in the border slave states. Invading armies also had to drop off large numbers of troops to guard their supply lines against cavalry and guerrilla raids. In Sherman’s campaign for Atlanta in 1864 the number of men protecting his rail communications 450 miles back to Louisville nearly
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