The Union used the Louisville and Nashville Railroad, and Morgan had identified two 500-foot (150 m) long trestle bridges at Muldraugh Hill that could be burnt.

They fought and defeated an Indiana cavalry detachment on Christmas Day at Bear Wallow, Barren County.

Harlan's men found part of Morgan's force under Colonel Basil W. Duke[note 4] near Boston at Lebanon Junction on the Rolling Fork River, on Monday, December 29.

[1][2] Duke made several spoiling attacks on Harlan's brigade to give his men time to escape across the Rolling Fork.

Morgan's men covered 500 miles (800 km) in the raid, killed or wounded 150 Union soldiers, and captured more than 1,800.

[3] Neighbouring Kentucky had declared neutrality at the start of the war but rejected the Confederacy and reaffirmed allegiance to the Union after a Confederate invasion by Major General Leonidas Polk in September 1861.

He was keen to hinder Union supply lines to the Army of the Cumberland in Tennessee and burnt the railway tunnels at Gallatin.

[7] Morgan's 4,000-strong force of cavalry, largely drawn from Kentucky regiments, with seven artillery pieces, left Alexandria, Tennessee, on December 22.

On Christmas Day, Thomas ordered John Marshall Harlan to travel by rail from Gallatin to search for Morgan's men and prevent him from progressing to Louisville.

With the remainder of his force, Morgan moved north and, on December 27, defeated the 91st Illinois Volunteer Infantry Regiment at Elizabethtown, taking 650 prisoners.

The force reached Muldraugh's Hill and overran the defensive stockades, protecting the two bridges and taking another 700 prisoners (including 27 officers).

[6] A party of Harlan's 11th Kentuckians discovered some of Morgan's men, numbering around 800 cavalry, at rest by the Rolling Fork River near Boston on December 29.

The raid provided Morgan with large quantities of captured stores and good-quality weapons to arm his entire force.

[14] Although work on repairing the railroad bridges did not commence until March 1863, Rosecrans' supply lines had generally reached pre-raid capacity by February 1.

[9] The raid diverted 7,300 Union soldiers from the December 31 – January 2 Battle of Stones River, where Bragg fought and was defeated by Rosecrans.