What was grants and Sherman's rationale for using the strategy of total war?

The purpose of the Total War Strategy was to wreck the economy of the Confederacy, and put a quick end to the war. The Union knew it had the advantage in terms of men and money. While northern farms had continued to produce food, the southerners had allowed greed to determine what was grown. As a result, breaking down the railroads in the south, meant that many of the soldiers as well as the civilians were hungry. The Union had also ended the prisoner of war exchange, because they came to realize that the release of prisoners, was allowing the South to go on fighting.