What were William Tecumseh sherman failures?

Answer 1

He failed to carry out Grant's orders to destroy the Army of Tennessee. However, his alternative plan to destroy the civilian infrastructure that supported the Confederate armies in the field probably ended the war quicker than by trying to pursue the Army of Tennessee through difficult mountain country.

Apart from that, he had certain failures of character and personality - rude and abrupt, half-mad anyway. But his reputation for brutality really reflected his desire to punish the traitorous states of Georgia and South Carolina, and there were very few casualties in that campaign.

He was a more creative strategist than he looked, and some have called him the father of modern warfare.