Enlisted in Company I, Iowa 36th Infantry Regiment on 04 Oct 1862.Mustered out on 24 Aug 1865 at Devall's Bluff, AR. Record also states that he was a POW.163

Holbrook, George. Age 19, Residence Appanoose County, nativity Iowa. Enlisted Aug. 11, 1862, as Wagoner. Mustered Oct. 4, 1862. Taken prisoner April 25, 1864, Mark's Mills, Ark. Returned to Company Feb. 25, 1865. Mustered out Aug. 24, 1865, Devall's Bluff, Ark. 298

The Battle of Marks' Mills (April 25, 1864), also known as the Action at Marks’ Mills, was fought in present-day Cleveland County, Arkansas, during the American Civil War….Following the battle, a Federal soldier in the 36th Iowa commented that, "The Rebs robbed nearly every man of us even to our chaplain. They stripped every stitch of clothes, even their shirts, boots and socks, and left the dead unburied and the woods on fire. Clothing was also pulled from the wounded as they begged for mercy. No respect was given for persons rank or age. Old Captain Charles Moss of the 43rd Indiana Infantry was marched bareheaded with his bald head and white locks and beard in the burning sun." Federal records indicate that some 190 infantrymen and cavalrymen escaped and made their way overland to report in at the Federal Depot at Pine Bluff or made it all the way to Little Rock. Colonel William McLean, commanding the brigade of which the three Federal regiments had been a part, wrote that some captured prisoners were stripped and forced to march into captivity completely naked. The Confederates reportedly left the Federal dead on the field for three days before any attempt was made to bury them, according to McLean.
Most of the soldiers captured from the 36th Iowa, 43rd Indiana, 77th Ohio and Peetz's Battery of the 1st Missouri Light Artillery were marched to Tyler, Texas, where they were incarcerated at a prison stockade at Camp Ford. Many died there over the next year from malnutrition and disease, but there were several successful escapes. Most of the prisoners remaining alive were released in 1865.299