What was the cause of Shermans march to sea?

Answer 1

His supply-line was getting too long and vulnerable, and he told Grant that he would not be able to pursue the Army of Tennessee into the mountains.

Instead he planned to conduct punitive raids on Georgia, living off the land as he went, and leaving George Thomas in Nashville to handle the Army of Tennessee.

Answer 2

Frequent attacks on his increasingly long and tenuous supply-line - a single-track railroad with 24 viaducts all the way back to Nashville. This made it hard for him to follow Grant's orders to seek out and destroy the Army of Tennessee.

Meanwhile he saw that Georgia had just brought in a good harvest, and realized that his army could live off the land.

So he decided to turn East across Georgia and relieve the blockade-runners' favourite ports of Savannah and Charleston.

Grant was sceptical at first, but eventually gave permission. Later Sherman admitted that he himself was nervous, partly because all the telegraph lines had been cut, and he would be incommunicado.

Still, it turned out a successful move, fatally destroying Southern morale.

Answer 3

His supply-line was getting too long and vulnerable, and he told Grant that he would not be able to pursue the Army of Tennessee into the mountains.

Instead he planned to conduct punitive raids on Georgia, living off the land as he went, and leaving George Thomas in Nashville to handle the Army of Tennessee.