William Tecumseh Sherman began in the regular army after graduating from West Point in 1840, serving in Florida and California. Civilian work in banking and law brought uneven success before appointment to lead the Louisiana State Seminary in 1859. He resigned when secession made continued service incompatible with his allegiance to the United States. Rejoining the army in 1861, he fought at First Bull Run and experienced a difficult period of command in Kentucky before rebuilding his standing through work with Ulysses S. Grant.

At Shiloh in 1862 Sherman helped hold and reorganize Union forces after surprise and severe losses. Service in the Vicksburg and Chattanooga campaigns gave him experience in coordinated operations and strengthened his relationship with Grant. In 1864 he led the advance through Georgia, manoeuvring against Joseph E. Johnston and later fighting John Bell Hood around Atlanta. The city's capture in September boosted Union confidence and helped the political setting of Lincoln's reelection. Military success depended on supply, engineering and the work of subordinate commanders as well as Sherman's direction.

The March to the Sea carried the army from Atlanta to Savannah, damaging railways, supplies and property intended to sustain Confederate resistance. It inflicted hardship on civilians and exposed the boundary between attacking military resources and coercing a population. Enslaved people seeking freedom followed the forces, but their treatment and protection were uneven. In 1865 Sherman advanced through the Carolinas and negotiated Johnston's surrender. His first agreement exceeded military terms and was rejected by Washington; a revised settlement followed. The episode shows that battlefield authority did not permit independent control of reconstruction.

After the war he held western commands and became commanding general of the army in 1869, serving until 1883. He supported campaigns forcing Native nations onto reservations and endorsed collective punishment in the Plains conflict, extending coercive methods into territorial expansion. His postwar leadership extended the army's role in conquest beyond Union victory. Memoirs shaped later interpretation of his campaigns, and he repeatedly rejected political candidacy. He died in 1891. His operational ability and contribution to defeating the Confederacy coexist with the destruction imposed on civilians and his leading role in the military dispossession of Indigenous peoples.