Short answers, pulled from the story.
On the 12th of August 1880, Sherman addressed a crowd of more than 10,000 people in Columbus, Ohio, saying "There is many a boy here today who looks on war as all glory, but, boys, it is all hell." A reporter for the Columbus Dispatch condensed those words to "Gen. Sherman said war was hell," and by June 1881 that version had entered mainstream usage.
Sherman's March to the Sea was a campaign beginning the 15th of November 1864, in which 62,000 Union soldiers marched from Atlanta to Savannah, Georgia, cutting loose from supply lines and living off the land. By Sherman's own estimate the march caused more than $100 million in property damage. Savannah fell on the 21st of December 1864.
While commanding Union forces in Kentucky in late 1861, Sherman sent exaggerated estimates of Confederate strength and made excessive requests for reinforcements, behavior that drew critical press reports. The Cincinnati Commercial described him as "insane". He was placed on leave by General Henry Halleck in December 1861 and sent home to Lancaster, Ohio, to recuperate, and he later admitted in private correspondence to having contemplated suicide during this period.
Sherman issued Special Field Orders No. 15 in January 1865, providing for the settlement of 40,000 freed slaves and Black refugees on land expropriated from white landowners in South Carolina, Georgia, and Florida. These orders became the basis of the claim that the Union government had promised freed slaves "forty acres and a mule." President Andrew Johnson revoked the orders later that year.
Sherman met Johnston at Bennett Place in Durham, North Carolina, on the 17th of April 1865, and agreed to terms covering both military and political matters. The Johnson administration rejected them because Sherman had acted without authority from Grant, President Johnson, or the Cabinet, and because Lincoln's assassination had hardened Washington's stance against rapid reconciliation. Secretary of War Edwin Stanton leaked Sherman's memorandum to The New York Times and implied Sherman may have been bribed.
British military historian B. H. Liddell Hart ranked Sherman as "the first modern general" and credited him with mastery of maneuver warfare, also called the indirect approach, in which a commander defeats the enemy through shock, disruption, and surprise while avoiding frontal attacks on fortified positions. Liddell Hart also claimed that his writings on Sherman influenced Heinz Guderian's doctrine of Blitzkrieg and George S. Patton's bold operational methods.