Enlisted as a private at Chicago, April, 1861, in 12th Illinois Infantry, being the second man on the enrollment list of those who enlisted in Chicago for the war. He was promoted to Sergeant, August, 1861; was with the 12th Illinois Regiment through all the campaigns under General Grant, in Kentucky and Tennessee, up to and including the Battle of Fort Donaldson, in February, 1862, at which battle, while storming the Fort and just before its surrender, he was badly shot in the right arm which caused his retirement from the 12th Illinois shortly thereafter. In August, 1862 he was appointed Captain of Company K, 82nd Illinois Infantry, in which Regiment he passed through the various campaigns and battles in Virginia, under Generals Burnside, Hooker and Meade. Captain Greenhut participated in the memorable Battle of Gettysburg, July 1st, 2nd and 3d, 1863. He was then transferred to the staff of Brigade Commander Hecker, being appointed Adjutant-General of the brigade. This brigade, after the Gettysburg Battle, Rosecrans who, with his army, was surrounded at was transferred to the Western army to relieve General Chattanooga, Tennessee. The brigade had a severe battle at Wauhatchie, near Chattanooga, in opening communications with Rosecrans. The same brigade also took a prominent part in the battles of Mission Ridge and Lookout Mountain, as well as shortly thereafter of that of Knoxville, Tennessee. On the retirement of General Hecker, in February, 1864, Captain Greenhut also resigned his position in the army; the following communication being handed him on his retirement, by General McGroarty, who succeeded in the command of the brigade:
"Headquarters 3d Brigade, 3d Division, 11th Corps.
Whiteside, Tenn., February 28th, 1864.
General order No. 9.
Captain Joseph B. Greenhut, of the 82nd Regiment Illinois Volunteers, having tendered his resignation, is, in pursuance of special order, No. 55, Headquarters Department of the Cumberland, February 24, 1864, relieved from duty as Assistant Adjutant-General of this Brigade, and Lieutenant Rudolph Muller is announced as his successor. In parting with Captain Greenhut, the Colonel commanding feels it both a duty and a pleasure to bear testimony to his diligence, zeal and fidelity in the performance of his duty in the office, as well as in the field, and he regrets to see so excellent and brave an officer as Captain Greenhut leave his command.
Matters of important character only could induce Captain Greenhut to leave the army in which he served three long and hard years, taking active part in all the most decisive battles east and west.
To be read on dress parade to the troops to-day.
By order of Colonel McGroarty,
Commanding Brigade and Post.
Rudolph Muller,
1st Lieutenant and A. A. A. General.
Captain Joseph B. Greenhut,
Assistant Adjutant-General, 3d Brigade."