Sherman had launched his grand offensive against the Army of Tennessee in early May. For more than two months, Sherman's forces, consisting of the Army of the Cumberland, the Army of the Tennessee and the Army of the Ohio, sparred with the Confederate Army of Tennessee, then under the command of General Joseph E. Johnston. Although the Southerners gained tactical successes at the Battle of New Hope Church, the Battle of Pickett's Mill, and the Battle of Kennesaw Mountain, they were unable to counter Sherman's superior numbers. Gradually, the Union forces flanked the Confederates out of every defensive position they attempted to hold. On July 8, Union forces crossed the Chattahoochee River, the last major natural barrier between Sherman and Atlanta.