In September 1864, after Union Gen. William T. Sherman defeated Confederate Gen. John Bell Hood at Atlanta, Hood led the Army of Tennessee northwest against Sherman's supply lines, then moved north into Tennessee, where Union Gen. John M. Schofield delayed him at Columbia and Spring Hill before falling back to Franklin. The bloodbath at Franklin on November 30 crippled Hood's force, but the Confederates followed Schofield to the outskirts of Nashville and Union Gen. George H. Thomas's strong defenses, where Hood's campaign ended when Thomas crushed his army on December 15-16. Before sunrise on December 17, 1864, in icy rain and dense fog, the exhausted soldiers of Hood's Army of Tennessee retreated south through this valley after their defeat at Nashville, pursued by Union forces. Confederate Gen. Edmund W. Pettus's brigade guarded the southwestern side of Hollow Tree Gap, also known as Holly Tree Gap, while Gen. Marcellus A. Stovall's brigade stood on the opposite side of the road with Capt. Hiram Bledsoe's Missouri artillery battery in support, and farther south Alabama and Louisiana regiments formed the reserve. Later that morning, as Confederate cavalry retreated through the gap, a Union cavalry brigade closed in from the north. The 19th Pennsylvania Cavalry and 10th Indiana Cavalry led the charge with sabers and carbines, but Pettus's and Stovall's rear guard quickly surrounded and outgunned the Federals, sending many back through the gap. Minutes later, detachments of the 10th Indiana Cavalry charged from the east, smashed through two Louisiana regiments, and flanked the rear guard. Fearing entrapment, the Confederates fought desperately to break out and continue retreating south. When the hour-long fight ended, the Federals had lost at least 22 killed and wounded and more than 60 captured, mostly from the Indiana and Pennsylvania regiments, while the Confederates lost about 250 captured, with an unknown number killed and wounded. This bloody clash was the first of several fights that ended after dark about fifteen miles south at the West Harpeth, the last significant battle in Williamson County.