For the past few months of 1863, the Civil War had started to turn in favor of the Federals. The Confederates lost the Battle of Gettysburg and their hope of advancing towards Washington, D.C. This is often called the High water mark of the Confederacy. The following day, the Confederates lost the city of Vicksburg to the Federals in a drawn out siege. Britain, having observed the Confederate defeat at Gettysburg, had just declined sending any aid for the rebels. In September 1863, Confederate General James Longstreet had been sent by Robert E. Lee from Virginia to assist Braxton Bragg in southeast Tennessee shortly before the Chickamauga Campaign. After Bragg besieged the city of Chattanooga, a detachment led by Longstreet was sent to prevent Ambrose E. Burnside from supporting the Union troops stationed in Chattanooga. After besieging Knoxville, Longstreet attempted to break into the city, but was soundly defeated at the Battle of Fort Sanders on November 29.