By nightfall on Sunday, September 20, 1863, more than two-thirds of the surviving Federal Army of the Cumberland had retreated from the Chickamauga battlefield through the narrow gap in Missionary Ridge known as McFarland's Gap. Protecting communications with the army's base at Chattanooga made the gap and the Dry Valley and McFarland Gap roads vital, since losing access to them could have brought disaster. Shortly after noon on the 20th, Union Major General William S. Rosecrans, concluding that the battle was lost after the Federal right and center were routed, reached the gap and learned from survivors of Major General James S. Negley's division that Negley was farther north rallying stragglers, deepening Rosecrans's fear of a severe defeat. Around 1:00 pm weary and often wounded Federal soldiers began streaming through the gap past overturned wagons, abandoned caissons, and other debris, and just north of it many demoralized infantrymen were stopped by the 15th Pennsylvania Volunteer Cavalry Regiment, the Anderson Cavalry, acting under Rosecrans's orders to halt stragglers before being sent to the rear. Many men rested on the farm of Xzanders G. and Lucy Ann B. McFarland, about a mile north, where the open ground allowed troops to be collected and reorganized after crossing terrain General Negley called broken, rugged, and densely wooded. Brigadier General Jefferson C. Davis rallied more than 1,000 men from his division there, and Major General Philip H. Sheridan brought about 1,500 survivors from the battlefield through the gap. By 3:00 pm the panic had begun to subside as officers rebuilt some semblance of an army, Davis placed an artillery battery to protect the gap, and fears of a Confederate cavalry attack lessened. Around 4:00 pm Negley, Davis, Sheridan, and Lieutenant Colonel Arthur C. Ducat of Rosecrans's staff met at the McFarland home to decide on a course of action, but after a heated discussion they could reach no agreement for common action. Some officers chose to return through the gap toward the battlefield to reinforce Union Major General George H. Thomas on Horseshoe Ridge, but none arrived in time. Thomas began withdrawing his troops around 5:30 pm, and almost all moved along the McFarland's Gap road before funneling through the gap, while the last to leave the battlefield around 10:00 pm was Colonel Daniel McCook, Jr's brigade. By the next morning McFarland's Gap and the McFarland farm were nearly deserted, and the bulk of the Federal army had reached Rossville safely and eventually Chattanooga.