By early May 1862, Union forces were positioned to invade Virginia at two places. Brig. Gen.Robert H. Milroy's column, its axis of march the Staunton-Parkersburg Turnpike, advanced from Cheat Mountain and occupied in succession Camp Allegheny, Monterey, McDowell, and Shenandoah Mountain. Retreating before the oncoming Federals, Confederate Brig. Gen. Edward "Allegheny" Johnson pulled back to Westview, six miles west of Staunton.
Seizing the initiative, Marshall bested Cox's 1st and 2nd brigades during three days of fighting, May 15 to May 17, in Mercer County, centering on Princeton Courthouse. There were 129 casualties in total.
Aftermath
Breaking contact with the Confederates on the night of May 17, Cox withdrew 20 miles (30 km). Col. George Crook, commanding Cox's 3rd brigade, marched to and occupied the city of Lewisburg, where on May 23 he defeated Brig. Gen. Henry Heth's larger brigade in the Battle of Lewisburg. Crook withdrew upon learning that Thomas J. "Stonewall" Jackson's army had routed a Union division at Winchester on May 25.
References
^Incomplete. There is a report from Marshall, but none from Wharton