The following is taken from New York in the War of the Rebellion, 3rd ed. Frederick Phisterer. Albany: J. B. Lyon Company, 1912. 

Colonel Rudolph Rosa received authority from the War Department, July 23, 1861, to recruit a regiment of infantry. The regiment was recruited and organized in New York city, composed mostly of Germans, and accepted by the State and numbered September 14, 1861. The companies were mustered in the service of the United States for three years; A July 29; B, C, D, E and F August 5, 14, 22, 27 and 30, respectively; G September 3; H September 6; I and K September 16, 1861. On the expiration of its term of service the men entitled thereto were discharged, and the regiment retained in service. While the latter was on its veteran furlough, May, 1864, the non-veterans were attached to the 36th Mass. Volunteers.
The regiment left the State September 14, 1861; served in Viele's, 1st, Brigade, T. W. Sherman's Expeditionary Corps, at and near Washington, D. C., from September 19, 1861; in the Department of the South from November, 1861; in the 2d Brigade, 2d Division, Department of the South, from December, 1861; in the 2d Brigade, 1st Division, 9th Corps, from July, 1862; in the 1st Brigade, 1st Division, 9th Corps, from September, 1862; in the 2d Brigade, 1st Division, 9th Corps, from November, 1862; in the 3d Brigade, 2d Division, 9th Corps, from June, 1862; in 2d Brigade, 2st Division, 9th Corps, from August, 1863; in Lockwood's Division, 5th Corps, from May 26, 1864; in the 2d Brigade, 4th Division, 5th Corps, Army of the Potomac, from May 30, 1864; in the 2d Brigade, 3d Division, 9th Corps, from June II, 1864; in the 2d Brigade, 1st Division, 9th Corps, from September, 1864; and it was honorably discharged and mustered out, under Lieut.-Col. Adolph Becker, July 28, 1865, at the Delancy House, D. C.
During its service the regiment lost by death, killed in action, 5 officers, 70 enlisted men; of wounds received in action, 3 officers, 31 enlisted men; of disease and other causes, 3 officers, 87 enlisted men; total, 11 officers, 188 enlisted men; aggregate, 199; of whom 15 enlisted men died in the hands of the enemy.

The following is taken from The Union army: a history of military affairs in the loyal states, 1861-65 -- records of the regiments in the Union army -- cyclopedia of battles -- memoirs of commanders and soldiers. Madison, WI: Federal Pub. Co., 1908. volume II. 

Forty-sixth Infantry.—Cols., Rudolph Rosa, Joseph Gerhardt, George W. Travers; Lieut.-Cols., Germain Metternich, Joseph Ger-hardt, George W. Travers, Ambrose Stevens, Adolph Becker; Majs., Joseph Gerhardt, Julius Parcus, Theodore Kohle, Ambrose Stevens, Peter French. The 46th, known as the Fremont Rifle regiment was composed of Germans, recruited in New York city, where the regiment was mustered into the U. S. service on July 29 to Sept. 16, 1861, for a three years' term. It left on Sept. 16, 800 strong, for Washington, where it was assigned to the 1st brigade, Sherman's division and quartered at Annapolis. Early in Novem-ber it was assigned to the Department of the South, embarked for Hilton Head, where it arrived on the 7th after a stormy voyage, and was stationed there until the following month, when it was moved to Tybee island, Ga., remaining there during the winter of 1861-62; and participating in the siege of Fort Pulaski. In June, 1862 it was sent to James island, S. C., where it was engaged on the 8th. It next was in action at Secessionville, and in July was ordered to return to Newport News, where it was assigned to the 2nd brigade, 1st division, 9th corps, with which it took part in the battles of Sulphur springs, Bull Run (second), Chantilly, South mountain and Antietam. In September, it was assigned to the 1st brigade, 1st division, 9th corps and in November, to the 2nd bri-gade once more. It was held in reserve at Fredericksburg, and then went into winter quarters at Falmouth. About the middle of June, 1863, the corps joined Gen. Grant at Vicksburg. There the regiment participated in the siege operations, then in the pursuit to Jackson and the fighting in that vicinity in July. In June it was transferred to the 3d brigade, 2nd division, and in August, returned to the 2nd brigade, 1st division. After the fall of Vicksburg the corps was ordered to Knoxville, being engaged on the march at Blue Springs and Campbell's station. The 46th was stationed at Knoxville during the siege, and during the winter the major portion of the regiment reenlisted and received veteran furlough. Upon the return of the 9th corps from Knoxville to Cincinnati, in April, 1864, the original members of the 46th not reenlisted proceeded to New York and were there mustered out on April 12. The veteran regiment served with the 2nd brigade, 4th division, 5th corps, Army of the Potomac, from May 30 to June 11, 1864; was then attached to the 2nd brigade, 3d division, 9th corps, with which it served until September, and was then transferred to the 2nd brigade, 1st division, 9th corps. It was active at the Wilderness, Spottsylvania, the North Anna, Totopotomy, and Cold Harbor; suffered heavy loss at Petersburg in the assaults of June 16-19, and at the mine explosion in July; participated in the actions at the Weldon railroad, Poplar Spring Church, Hatcher's run, Fort Stedman, and the final assault on April 2, 1865. Soon after the fall of Petersburg, the regiment was ordered to Washington, where it was mustered out July 28, 1865. The total loss of the regiment was 327 killed, wounded and missing, 109 members dying from wounds during the term of service and 89 from other causes.