​​The Thirty-fifth Regiment Indiana Infantry was organized as an Irish regiment, to be composed of Irishmen exclusively. It was mustered in at Indianapolis on December 11, 1861, for three years' service, with John C. Walker as Colonel, and was sent on the 13th to Kentucky, where it remained at Bardstown for six weeks in camp of instruction, and went from thence to Bowling Green and from thence to Nashville, Tenn. Subsequent to the organization of the Thirty-fifth Indiana, the second Irish regiment to be known as the Sixty-first Regiment Indiana Infantry was partially organized and mustered into service, but a sufficient number, however, failing to enlist to complete the organization, the men that had enlisted for the Sixty-first Regiment were sent to Tennessee in charge of Col. Bernard F. Mullen and consolidated with the Thirty-fifth on May 22, 1862, and Colonel Mullen accepted the position of Lt. Colonel of the Thirty-fifth, but subsequently, on August 7, 1862, was commissioned and mustered as Colonel of the thirty-fifth Indiana. During the summer of 1862 the regiment was sent from Nashville to McMinnville, Tenn., where it camped until September, 1862, when it returned to Nashville, rejoining Buell's Army at that place and marching with it to Louisville, Ky. Where it became part of Stanley Matthews brigade, Van Cleve's Division, Crittenden's Corps. From Louisville the regiment moved with Buell's Army in the pursuit of Bragg through Kentucky, participating in the battle of Perryville and in the skirmishes on the march subsequent thereto, until Bragg was driven from Kentucky, when it returned to Nashville under Rosecrans. It took part in the skirmishes and foraging expeditions during the month of December., and on the 9th of December, at Dobbin's Ford, near La Vergne, while on a foraging expedition, it had a severe skirmish with the enemy, losing five killed and thirty-five wounded. When Rosecrans advanced on Murfreesboro this regiment accompanied its brigade in that advance and participated in the battle of Stone's River on December 31, 1862, and January 1, 2 and 3, 1863. In the battle of Stone's River the position of the regiment was on the extreme left of Rosecrans' Army, where it was engaged in the most severe fighting of the battle. In the battle it lost 29 killed, 72 wounded and 33 missing, a total loss of 134, this being one-third of the entire number of the regiment present and engaged in the battle. The Thirty-fifth remained in the vicinity of Murfreesboro until Rosecrans' campaign through Middle Tennessee, in which it took a prominent part. It marched with its brigade in the advance upon Chattanooga and was present and took part in the battle of Chickamauga on the 19th and 20th of September, sustaining heavy losses. While in camp at Shell Mound, Tenn., the regiment re-enlisted as a veteran regiment on December 16, 1863, and returned to Indianapolis on veteran furlough. The regiment returned to Tennessee in February, 1864, and went into camp at Blue Springs until the opening of the campaign of 1864 of Sherman. On the Atlanta campaign this regiment was attached to the Second Brigade (Whitaker), First Division (Stanley), Fourth Corps (Howard). It participated in all of the marches, battles, skirmishes and scouts of that celebrated and now historical campaign. In the battle of Kenesaw Mountain on June 20, 1864, while the regiment was in the front line, a very fierce and unexpected attack was made by the enemy in their front, and the regiment was temporarily thrown into confusion. It rallied, however, very quickly and the fight became a most desperate hand-to-hand conflict. The men of the Thirty-fifth used their muskets as clubs, and bayoneted the enemy whenever opportunity offered; finally, reinforcements having been sent, the enemy was driven back. In this engagement the Thirty-fifth lost eleven killed, including its commanding officer, Major John P. Dufficy, and forty-five wounded. On the 4th of July, 1864, when Sherman's lines were advancing near Marietta, Ga., this regiment, while on duty as part of the skirmish line, made a charge and captured the enemy's rifle pits with twenty-eight prisoners. This charge was successfully made notwithstanding the fact that the regiments to the right and left of the Thirty-fifth were repulsed, leaving the Thirty-fifth exposed to a fire from both flanks. The regiment was in the battle of Jonesboro taking an active part, also at Lovejoy's Station, the final battle of the campaign. It returned to Atlanta with Sherman's Army and remained there until the army started in pursuit of General Hood, who had flanked Sherman and was marching Northward. It remained with the Fourth Corps on the campaign back to Nashville and took part in the battles of Columbia, Spring Hill and Franklin. At Franklin, Tenn. the regiment received about 400 drafted men and substitutes, and with these new men was placed in the front line in the battle of that place on the 30th of November, 1864. The drafted men and substitutes did their part well towards sustaining the fighting reputation of the regiment. Notwithstanding several severe charges were made upon their position of the line, the enemy was repulsed and driven back in each charge. Marching back to Nashville after the battle of Franklin, the regiment was engaged in the Battle of Nashville for two days, taking a conspicuous part. In the rout and pursuit of Hood this regiment participated until it reached Duck River, when it was detached from its brigade and assigned to the charge of the pontoon train. When the Fourth Corps moved to Huntsville, Ala., to Knoxville, Tenn., in March, 1865 this regiment went with its corps, and returned to Nashville after Lee's surrender, in 1865. In June, 1865, it was transferred to Texas with the Fourth Corps, where it remained on duty with Sheridan's Army until September, when it was mustered out of service and returned home, reaching Indianapolis on the 20th of October, 1865. On the Atlanta campaign and the return, including the battle of Nashville, the regiment lost in killed and wounded 139 men.

 
William H.H. Terrell, Report of the Adjutant General of the State of Indiana, Vol. II 1861-1865, Indianapolis: State Printer, 1865.