Burnside settled into entrenchments around the city, which Longstreet besieged. Longstreet soon learned that Bragg had been defeated at Chattanooga on November 25, and that William Tecumseh Sherman's men were marching to relieve Burnside. He decided to risk a frontal attack on Union entrenchments before they arrived. On November 29, he sent his troops forward at the Battle of Fort Sanders. The attack was repulsed, and Longstreet was forced to retreat. When Bragg was defeated by Grant, Longstreet was ordered to join forces with the Army of Tennessee in northern Georgia. He demurred and began to move back to Virginia, soon pursued by Sherman. Longstreet defeated federal troops in an engagement at Bean's Station on December 14 before the armies went into winter quarters. The greatest effect of the campaign was to deprive Bragg of troops he sorely needed in Chattanooga. Longstreet's second independent command (after Suffolk) was a failure and his self-confidence was damaged. He reacted to the failure of the campaign by blaming others. He relieved Lafayette McLaws from command and requested the court martial of Robertson and Law. He also submitted a letter of resignation to Adjutant General Samuel Cooper on December 30, 1863, but his request to be relieved was denied.