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. In September 1862, Lincoln issued the Emancipation Proclamation, which made ending slavery a war goal. To the west, the Union destroyed the Confederate river navy by summer 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, leading 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 capitol of Richmond.