Thomas Sidney Mills was born in Early County, Georgia on July 20th, 1842, and prior to the war, he resided as a farmer in Dale County, Alabama. His parents were Thomas and Eliza Jane Forbes Mills. He had three sisters, Lucy Forbes Mills, Leonora Alice Mills, and Catherine Elizabeth Mills, and one older brother, Wesley Berryan Mills. Six months following Alabama’s  secession from the United States and joining of the Confederate States, Thomas enlisted at the age of eighteen in Company E, “Beauregards” 15th Alabama Infantry on July 3rd, 1861 at Westville, Alabama. His older brother, Wesley, also joined the 15th Alabama, commissioned as a 2nd Lieutenant for Company E, “Beauregards”. One of the first significant actions the 15th Alabama was involved in during the Valley Campaign of 1862 was the Battle of Cross Keys on June 8th, 1862. It was during this engagement that Thomas’ brother, Wesley, was shot through the head and killed, becoming the first officer in the 15th Alabama to die as a result of enemy fire in the war. However, Thomas had to carry on with the rest of his company and regiment, and he would not go unscathed as a result of the war. During the Maryland Campaign of 1862, Thomas was wounded at the Battle of Antietam on September 17th, 1862 during General Robert E. Lee’s first march into the North. Almost a year later, Thomas was again present with the 15th Alabama as General Lee marched into the Pennsylvania, engaging the Federals at Gettysburg. On July 2nd, 1863, Thomas, the 15th Alabama, and the rest of Evander Law’s Alabama Brigade was placed on the extreme right of General Lee’s battle line, eventually being tasked with assaulting up Little Round Top. During these attacks, Thomas was wounded for a second time. He recuperated and once again rejoined the 15th Alabama, being promoted to Corporal for his actions at Gettysburg. He was promoted again to the rank of Sergeant on August 1st, 1864. A couple weeks later, for a third time, Thomas was wounded in the shoulder at the Second Battle of Deep Bottom on August 16th, 1864. However, this wound was much more severe than the others he had sustained at Antietam and Gettysburg, and it sidelined him from the front lines around Petersburg and Richmond for a couple months.

Thomas did return and rejoin the 15th Alabama before the Appomattox Campaign. As Petersburg and Richmond fell to Federal armies, Thomas was present as Lee’s Army of Northern Virginia picked up the pieces and attempted to march south towards North Carolina with the hopes of joining forces with General Joseph Johnson’s western Confederate army. Due to the 15th Alabama belonging to William Perry’s Alabama Brigade, Charles Field’s Division, James Longstreet’s 1st Corps, Thomas was in front of Lee’s army, and not engaged in many of the rear action fights early in the campaign, nor at the Battle of Sailor’s Creek on April 6th, 1865. Near Farmville, General John Gordon’s 2nd Corps took the lead of the marching columns, Longstreet now covering the rear. While Gordon’s 2nd Corps engaged the Federals at Appomattox Court House on the morning of April 9th, Thomas and the 15th Alabama were fighting as the rear guard at New Hope Church until flags of truce and a cease fire had been ordered to allow the commanding generals to meet and discuss surrender. Thomas was surrendered with 218 others that remained in the 15th Alabama at Appomattox Court House, April 9th, 1865. After receiving his parole pass, he was allowed to go home to Dale County, Alabama. After the war, Thomas continued to live in Dale County as a farmer and warehouseman. He married Lavinia Pouncey, fathered eight children, and at the age of 59, Thomas died on March 21st, 1902 at Clayhatchee, Alabama.