The Battle of Shiloh.
In this critical battle, with Cincinnati as its prize, Sherman saw the carnage of the Civil War first hand. Gruesome injuries and death surrounded him and Sherman himself nearly died. Sherman drew from this the conclusion that the only way to end the war was to make the slave owning class pay the price of defending slavery, instead of being allowed to send non-slave owning whites to the front to fight in their stead.
Grant's experience was different. He was behind the front and observed only the tactical situation as presented to him by messengers. His conclusion by battles end, based on his experience, was that the way to win was to throw waves of reserves into the fray, who could use superior numbers and freshness of legs to defeat the enemy. Both generals incorporated their lessons in their future tactics. Grant ran the meat grinder in Northern Virginia, losing huge numbers of men each time he went out, totally reliant on frontal attack. Sherman however, rarely again engaged enemy forces head on, preferring to destroy communication lines, rail lines, supply depots, and other critical military infrastructure on his March to the Sea.
While Grant became a great American hero, it was Sherman who was the more humane commander, and the more effective strategist. Largely because of Sherman's demonized reputation in the south after the war, his ideas were abandoned by future military leaders, a disproportionate number of whom came from the south, in favor of an approach closer to that of Grant and Lee, traditional Total War.
well maybe it was humane and maybe tactics but he was not very humane in that march you know