James P. Brownlow served in several positions in the Union Army, finishing the war as colonel of the 1st Tennessee Cavalry Regiment.

Union cavalry in Tennessee, in addition to participating in crucial organized battles of the war, "primarily meant almost endless skirmishing with partisans, guerrillas, and bushwackers, as well as with the Rebel raiders of John Hunt Morgan, Joseph Wheeler, and Nathan Bedford Forrest, who frequently recruited and supplied themselves from behind enemy lines.

[4] In accord with his father and a majority of the residents of eastern Tennessee,[5] James P. Brownlow remained loyal to the Union after the outbreak of the American Civil War.

[6][7] Brownlow's regiment was first organized in November 1861 at Camp Garber near Flat Lick, Kentucky, as the 4th Tennessee Infantry (Union).

On July 30, 1862, Major General Don Carlos Buell declined Military Governor of Tennessee Andrew Johnson's request to mount the regiment.

[10] On September 17, 1862, General Morgan abandoned Cumberland Gap because Confederate forces were converging on his men and they were in danger of being cut off from supplies and reinforcements.

[22] In late February, Brownlow led a reconnaissance to Triune, Tennessee, 21 miles (34 km) south-east of Nashville, after being temporarily assigned as the only cavalry regiment in Brigadier General James B. Steedman's division.

[24] According to a history of the 14 Union cavalry regiments from Tennessee:[1] Instead of going himself, Johnson, as was his habit, deployed a detachment under Lieutenant Colonel Brownlow.

Riding out at night, Brownlow forded the Harpeth River and found only small enemy squads toward Chapel Hill.

As Brownlow returned at dawn near the Harpeth, graycoats concealed along the pike fired, yelled, and rushed his rear guard, hoping to panic the entire column.

[16] In that month, Major General William Rosecrans began the Tullahoma Campaign which forced the Confederates to abandon that town and retreat to Chattanooga.

[16][29] A few days later, on October 12, 1863, Campbell's brigade made an attack at nightfall in the rain on Confederate Brigadier General Philip D. Roddey's Division, which soon disengaged and moved to a camp away from the battlefield.

[30] On December 15, the division reached Knoxville and McCook allowed the 1st Tennessee Cavalry to be the first regiment to enter the home town of Colonel Brownlow and many of the men.

Then, Colonel Campbell ordered the 1st Tennessee Cavalry to charge the Confederates on the right of a brick house, a prominent feature on the field.

Confederate Brigadier General William T. Martin marched his army across the country from Dandridge and went into camp near Fair Garden, Tennessee.

This unexpected movement of Longstreet's cavalry made it necessary to push forward the divisions of McCook and Wolford from Knoxville to support the right wing.

Campbell's brigade moved to strike the Confederates behind the east fork of the Pigeon River but after an artillery duel, nightfall halted the engagement.

[38] In the renewed engagement of January 27, 1864, as nightfall approached, Colonel Brownlow became separated from his men while pursuing Confederates who had been driven from the field.

He hid his grade (rank) and identity from his captors, claiming to be a private, and managed to bribe a guard with a gold watch to permit him to escape.

[45] On June 3, 1865, Colonel Brownlow led his men on a charge which drove back a Confederate force holding a high hill at Acworth, Georgia.

[49][50] On July 4, 1864, General Johnston pulled his forces back over the Chattahoochee River and had almost all the ferry boats for miles in either direction destroyed.

[53] Colonel Joseph Dorr of the 8th Iowa Cavalry Regiment, acting commander of the brigade, arrived on the scene and ordered Brownlow to complete the mission.

[55] After swimming back across the river, Brownlow's men expressed even more admiration for their commander who was willing to share the hardships and dangers of the mission and not just to order others to carry out the unusual and uncomfortable task.

"[58] On July 9, 1864, General Johnston pulled back to Peachtree Creek and the Union forces soon crossed the Chattahoochee River near Power's Ferry.

[60] Hood attacked the Union Army positions several times and suffered numerous casualties over the next several days before taking a more defensive posture.

Now part of Brigadier General John T. Croxton's brigade, the 1st Tennessee Cavalry reached Palmetto Station, Georgia and about 3:00 p.m. and began to destroy telegraph facilities, the depot and supplies.

As the war wound down to a conclusion, the 1st Tennessee Cavalry made a reconnaissance from Waterloo, Alabama as far as Corinth, Mississippi, starting on January 27, 1865.

[82] On January 13, 1866, President of the United States Andrew Johnson nominated Brownlow for the award of the honorary grade of brevet brigadier general of volunteers, to rank from March 13, 1865.

In December 1866, Brownlow received an appointment at the grade of captain in the 8th United States Cavalry Regiment of the Regular Army.

[3][94] One obituary described him as a "man of Herculean stature, measuring six feet six inches in height, [he] was in every respect a gallant soldier and courteous gentleman.