The Horse Artillery Brigade of the Army of the Potomac was a brigade of various batteries of horse artillery during the American Civil War. Made up almost entirely of individual, company-strength batteries from the Regular Army's five artillery regiments, the Horse Artillery operated under the command umbrella of the Cavalry Corps. The Horse Artillery differed from other light artillery (also known as "mounted" artillery) in that each member of the unit traveled on his own horse, rather than the traditional light artillery practice of "drivers" riding horses pulling the guns, while the cannoneers rode on the limbers and caissons. Ordinarily, though, the cannoneers traveled on foot behind their respective gun. But, with each man on his own horse, the unit could travel faster and more efficiently. It was the brainchild of former artillery captain and Brig. Gen. William Farquhar Barry, Chief of Artillery for the Army of the Potomac, in 1861. With such a large percentage of the U.S. Horse Artillery being artillery batteries from the regular U.S. Army, it developed a superb reputation for military efficiency, accuracy of fire, and command presence in the field and in battle. These mobile artillery units were typically equipped with 3-inch Ordnance rifles, known for their reliability and accuracy. Originally under the direct command of Lt. Col. (and future Brigadier General) William Hays, and later under the two-brigade command of captains James Madison Robertson and John C. Tidball, the Horse Artillery served with distinction during most of the major engagements in the Eastern Theater. Tidball's brigade later was commanded by Capt Dunbar R. Ransom. It is notable that each of these men - Barry, Hays, Robertson, and Tidball - came from the officers corps of the 2nd Regiment of Artillery. One of their chief champions, Henry Jackson Hunt, commanded the Reserve Artillery in the Army of the Potomac, and was also an officer of the 2nd U.S. Artillery.

Organization

1862 - Peninsula Campaign

Commander: Lieutenant Colonel William Hays, USV (Captain, USA, 2nd U.S. Artillery), of Tennessee Battery A, 2nd U.S. Artillery (2nd Regiment of Artillery) Commander: Captain John C. Tidball, USA, of Ohio Battery B & L, 2nd U.S. Artillery Commander: Captain James Madison Robertson, USA, of New Hampshire Battery M, 2nd U.S. Artillery Commander: Captain Henry Benson, USA, of New Jersey Battery C, 3rd U.S. Artillery Commander: Captain Horatio Gates Gibson, USA, of Pennsylvania

1863 - Gettysburg Campaign

First Brigade, Horse Artillery

Commander: Captain James Madison Robertson, USA Acting Assistant Adjutant General: First Lieutenant J.H. Bell, 6th New York Cavalry Batteries of the First Brigade: 9th Michigan Battery, US Volunteers (6 - 3-inch Ordnance rifles) Commander: Captain Jabez James Daniels, USV Independent Battery, 6th New York Light Artillery, US Volunteers (6 - 3-inch Ordnance rifles) (formerly the Artillery Company K, 9th New York State Militia, and the 83rd New York Infantry Regiment) Commander: Captain Joseph W. Martin, USV Batteries B & L, 2nd US Artillery (6 - 3-inch Ordnance rifles) Commander: First Lieutenant Edward Heaton, USA Battery M, 2nd US Artillery (6 - 3-inch Ordnance rifles) Commander: First Lieutenant Alexander Cummings McWhorter Pennington, Jr., USA Battery E, 4th US Artillery (4 -3-inch Ordnance rifles) Commander: First Lieutenant Samuel Sherer Elder, USA

Second Brigade, Horse Artillery

Commander: Captain John Caldwell Tidball, USA Batteries of the Second Brigade: Battery E & G, 1st US Artillery (4 - 3-inch Ordnance rifles) Commander: Captain Alanson Merwin Randol, USA 1st U.S. Light Artillery, Battery K (6 - 3-inch Ordnance rifles) Commander: Captain William Montrose Graham, USA Battery A, 2nd U.S. Artillery (6 - 3-inch Ordnance rifles) Commander: Second Lieutenant John Haskell Calef, USA Battery C, 3rd US Artillery (6 - 3-inch Ordnance Rifles)* Commander: First Lieutenant William Duncan Fuller, USA Light Battery H, 3rd Pennsylvania Heavy Artillery, US Volunteers (2 - 3-inch Ordnance rifles) Commander: Captain William D. Rank, USV

• Note: Battery C, 3rd US Artillery was not present during the battle of Gettysburg

1864 - Overland Campaign

The Horse Artillery remained organized into two brigades until June, when it was reduced to one. The units that were cut from the ranks left their best equipment with the remaining units, and reported to Washington, DC for further orders, elsewhere. The following are the final list of command and staff and order of battle of the larger organization and the list for the reduced roster.

January – June, 1864

First Brigade, Horse Artillery

Commander: Captain James Madison Robertson, USA (Brevet Colonel) Quartermaster: Captain William Goldie, USV (formerly Captain, 56th Illinois Infantry) Commissary of Subsistence: Captain Henry Loud Cranford, USV (formerly First Lieutenant, 84th New York Infantry) Organization: 9th Battery, Michigan Light Artillery Commander: Captain Jabez Daniels, USV 6th Independent Battery, New York Light Artillery Commander: Captain Joseph W. Martin, USV Batteries B & L, 2nd U.S. Artillery Commander: First Lieutenant Edward Heaton, USA Battery D, 2nd U.S. Artillery Commander: First Lieutenant (Brevet Major) Edward Bancroft Williston, USA Battery M, 2nd U.S. Artillery Commander: First Lieutenant (Brevet Major) Alexander Cummings McWhorter Pennington, Jr., USA Battery A, 4th U.S. Artillery Commander: First Lieutenant (Brevet Captain) Rufus King, Jr., USA Battery E, 4th U.S. Artillery Commander: Captain Samuel Elder, USA

Second Brigade, Horse Artillery

Commander: Captain John Caldwell Tidball, USA (Brevet Lieutenant Colonel, USA; Colonel, 4th New York Artillery, USV) Quartermaster: Captain Ira F. Payson, USV (died, July 30, 1864) Commissary of Subsistence: First Lieutenant (Brevet Captain) William Murray Maynadier, USA Organization: Battery E & G, 1st U.S. Artillery Commander: First Lieutenant Frank Sands French, USA Battery K, 1st U.S. Artillery Commander: Captain (Brevet Lieutenant Colonel) William Montrose Graham, USA Battery A, 2nd U.S. Artillery Commander: First Lieutenant Robert Clarke, USA Section Chiefs: First Lieutenants John H. Calef, USA; N.A. Cameron, USV (TDY from 4th New York Heavy Artillery); and B.J. (Benjamin Franklin) Littlefield, USV (former US Sharpshooter, on TDY from 4th New York Heavy Artillery) Battery G, 2nd U.S. Artillery Commander: First Lieutenant (Brevet Major) John Hartwell Butler, USA Battery C, 3rd U.S. Artillery Commander: First Lieutenant (Brevet Major) William Duncan Fuller, USA

From June 1864

Horse Artillery Reserve, Army of the Potomac

Commander – Captain (Brevet Colonel) James M. Robertson, USA Organization: Batteries H & I, 1st U.S. Artillery Commander: Captain (Brevet Major) Alanson M. Randol, USA Battery K, 1st U.S. Artillery Commander: First Lieutenant (Brevet Major) John Egan, USA Battery A, 2nd U.S. Artillery Commander: First Lieutenant Robert Clarke, USA Batteries B&L, 2nd U.S. Artillery Commander: First Lieutenant Edward Heaton, USA Battery D, 2nd U.S. Artillery Commander: First Lieutenant (Brevet Lieutenant Colonel) Edward B. Williston, USA Battery M, 2nd U.S. Artillery Commander: First Lieutenant (Brevet Major) Alexander C.M. Pennington, Jr., USA Batteries C, F,&K, 3rd U.S. Artillery Commander: First Lieutenant (Brevet Major) James Rigney Kelly, USA (formerly enlisted Engineers Artificer and later enlisted 3rd Artillery Sergeant) Batteries C&E, 4th U.S. Artillery Commander: First Lieutenant Charles Lane Fitzhugh, USA, (later Colonel, 6th New York Cavalry and Brevet Brigadier General, USA and USV)

Units separated & sent to Washington, D.C. for further orders

Batteries E & G, 1st U.S. Artillery Commander: First Lieutenant David Essex Porter, USA Battery G, 2nd U.S. Artillery Commander: First Lieutenant (Brevet Major) William Neil Dennison, USA Battery A, 4th U.S. Artillery Commander: First Lieutenant Rufus King, Jr., USA 6th New York Independent Battery Commander: Captain Joseph W. Martin, USV

1865

By 1865, the Horse Artillery Brigade still existed on paper, but the various units were dispersed and assigned to a number of commands, as was the typical practice of regular foot artillery in the field.