After successfully breaking the Confederate siege at Chattanooga near the end of 1863, William Tecumseh Sherman united several Union armies in the Western theater for the Atlanta Campaign, forming one of the biggest armies in American history. After detaching troops for essential garrisons and minor operations, Sherman assembled his nearly 100,000 men and in May 1864 began his invasion of Georgia from Chattanooga, Tennessee, where his forces spanned a line roughly 500 miles wide. Sherman set his sights on the Confederacy's last major industrial city in the West and General Joseph E. Johnston's Army of Tennessee, which aimed to protect it. Atlanta's use to the Confederacy lay in its terminus for three major railroad lines that traveled across the South: the Georgia Railroad, Macon and Western, and the Western & Atlantic. U.S. Lieutenant General Ulysses S. Grant knew this, sending Major General William Tecumseh Sherman's Division of the Mississippi towards Atlanta, with specific instructions, "get into the country as far as you can, inflicting all the damage you can against the war revenues." The city's ability to send supplies to Lee's Army of Northern Virginia made Atlanta all the more important. The people of Atlanta clearly identified their own role in the struggle, as the Atlanta Daily Appeal noted, "The greatest battle of the war will probably be fought in the immediate vicinity of Atlanta. Its results determines that of the pending Northern Presidential election. If we are victorious the Peace party will triumph; Lincoln's Administration is a failure, and peace and Southern independence are the immediate results." It would fall upon Sherman's forces in the West to deliver the necessary victory. Johnston's army of 50,000 found itself confronted by almost double its numbers, and General Johnston began gradually retreating in the face of Sherman's forces, despite repulsing them in initial skirmishes at Resaca and Dalton. The cautious Johnston was eventually sacked and replaced by the more aggressive John Bell Hood once the Confederate army was back in Atlanta. Taking command in early July 1864, Hood lashed out at Sherman's armies with several frontal assaults on various portions of Sherman's line, but the assaults were repulsed, particularly at Peachtree Creek on July 20, where Thomas's defenses hammered Hood's attack. At the same time, Sherman was unable to gain any tactical advantages when attacking north and east of Atlanta. In August, Sherman moved his forces west across Atlanta and then south of it, positioning his men to cut off Atlanta's supply lines and railroads. When the Confederate attempts to stop the maneuvering failed, the writing was on the wall. On September 1, 1864, Hood and the Army of Tennessee evacuated Atlanta and torched everything of military value. On September 3, 1864, Sherman famously telegrammed Lincoln, "Atlanta is ours and fairly won." Two months later, so was Lincoln's reelection.