William Tecumseh Sherman ( tih-KUM-s; February 8, 1820 February 14, 1891) was an American soldier, businessman, educator, and author. He served as a general in the Union Army during the American Civil War (18611865), achieving recognition for his command of military strategy as well as criticism for the harshness of the scorched-earth policies that he implemented against the Confederate States. British military theorist and historian B. H. Liddell Hart declared that Sherman was "the first modern general".Born in Ohio into a politically prominent family, Sherman graduated in 1840 from the United States Military Academy at West Point. He interrupted his military career in 1853 to pursue private business ventures, without much success. In 1859, he became superintendent of the Louisiana State Seminary of Learning & Military Academy (now Louisiana State University), a position from which he resigned when Louisiana seceded from the Union. Sherman commanded a brigade of volunteers at the First Battle of Bull Run in 1861 before being transferred to the Western Theater. He was stationed in Kentucky, where his pessimism about the outlook of the war led to a breakdown that required him to be briefly put on leave. He recovered by forging a close partnership with General Ulysses S. Grant. Sherman served under Grant in 1862 and 1863 in the Battle of Fort Henry and the Battle of Fort Donelson, the Battle of Shiloh, the campaigns that led to the fall of the Confederate stronghold of Vicksburg on the Mississippi River, and the Chattanooga campaign, which culminated with the routing of the Confederate armies in the state of Tennessee.

In 1864, Sherman succeeded Grant as the Union commander in the Western Theater. He led the capture of the strategic city of Atlanta, a military success that contributed to the re-election of President Abraham Lincoln. Sherman's subsequent march through Georgia and the Carolinas involved little fighting but large-scale destruction of cotton plantations and other infrastructure, a systematic policy intended to undermine the ability and willingness of the Confederacy to continue fighting. Sherman accepted the surrender of all the Confederate armies in the Carolinas, Georgia, and Florida in April 1865, but the terms that he negotiated were considered too generous by U.S. Secretary of War Edwin Stanton, who ordered General Grant to modify them.

When Grant became president of the United States in March 1869, Sherman succeeded him as Commanding General of the Army. Sherman served in that capacity from 1869 until 1883 and was responsible for the U.S. Army's engagement in the Indian Wars. He steadfastly refused to be drawn into party politics and in 1875 published his memoirs, which became one of the best-known first-hand accounts of the Civil War.

The American Civil War (April 12, 1861 – May 9, 1865; also known by other names) was a civil war in the United States between the Union (states that remained loyal to the federal union, or "the North") and the Confederacy (states that voted to secede, or "the South"). The central cause of the war was the status of slavery, especially the expansion of slavery into territories acquired as a result of the Louisiana Purchase and the Mexican–American War. On the eve of the Civil War in 1860, four million of the 32 million Americans (~13%) were enslaved black people, almost all in the South.The practice of slavery in the United States was one of the key political issues of the 19th century. Decades of political unrest over slavery led up to the Civil War. Disunion came after Abraham Lincoln won the 1860 United States presidential election on an anti-slavery expansion platform. An initial seven southern slave states declared their secession from the country to form the Confederacy. Confederate forces seized federal forts within territory they claimed. The last-minute Crittenden Compromise tried to avert conflict but failed; both sides prepared for war. Fighting broke out in April 1861 when the Confederate army began the Battle of Fort Sumter in South Carolina, just over a month after the first inauguration of Abraham Lincoln. The Confederacy grew to control at least a majority of territory in eleven states (out of the 34 U.S. states in February 1861), and asserted claims to two more. Both sides raised large volunteer and conscription armies. Four years of intense combat, mostly in the South, ensued.

During 1861–1862 in the war's Western Theater, the Union made significant permanent gains—though in the war's Eastern Theater the conflict was inconclusive. On January 1, 1863, Lincoln issued the Emancipation Proclamation, which made ending slavery a war goal, declaring all persons held as slaves in states in rebellion "forever free." To the west, the Union destroyed the Confederate river navy by the summer of 1862, then much of its western armies, and seized New Orleans. The successful 1863 Union siege of Vicksburg split the Confederacy in two at the Mississippi River. In 1863, Confederate General Robert E. Lee's incursion north ended at the Battle of Gettysburg. Western successes led to General Ulysses S. Grant's command of all Union armies in 1864. Inflicting an ever-tightening naval blockade of Confederate ports, the Union marshaled resources and manpower to attack the Confederacy from all directions. This led to the fall of Atlanta in 1864 to Union General William Tecumseh Sherman and his march to the sea. The last significant battles raged around the ten-month Siege of Petersburg, gateway to the Confederate capital of Richmond.

The Civil War effectively ended on April 9, 1865, when Confederate General Lee surrendered to Union General Grant at the Battle of Appomattox Court House, after Lee had abandoned Petersburg and Richmond. Confederate generals throughout the Confederate army followed suit. The conclusion of the American Civil War lacks a clean end date: land forces continued surrendering until June 23. By the end of the war, much of the South's infrastructure was destroyed, especially its railroads. The Confederacy collapsed, slavery was abolished, and four million enslaved black people were freed. The war-torn nation then entered the Reconstruction era in a partially successful attempt to rebuild the country and grant civil rights to freed slaves.

The Civil War is one of the most studied and written about episodes in the history of the United States. It remains the subject of cultural and historiographical debate. Of particular interest is the persisting myth of the Lost Cause of the Confederacy. The American Civil War was among the earliest to use industrial warfare. Railroads, the telegraph, steamships, the ironclad warship, and mass-produced weapons saw wide use. In total the war left between 620,000 and 750,000 soldiers dead, along with an undetermined number of civilian casualties. President Lincoln was assassinated just five days after Lee's surrender. The Civil War remains the deadliest military conflict in American history. The technology and brutality of the Civil War foreshadowed the coming World Wars.