Fleet support turns the march into a siege threat

The campaign's central logistics bargain was to remain light enough to move inland, then become heavy enough to take a port. As at Vicksburg, land manoeuvre only worked because a fleet could bring the artillery and supplies needed at the destination. Capturing Savannah would connect Sherman to sea-borne support before his mobile army exhausted its resources. The port and its railways would also provide a secure base for an advance north into the rear of Virginia. By crossing Georgia from Atlanta to the Atlantic, Sherman physically divided Confederate territory and made its regions less able to support one another.