By early May 1862, Union forces in today's West Virginia were positioned to breach the Alleghenies and debouch into Virginia's Great Valley at two points more than 100 miles apart. Big. Gen. Robert H. Milroy's column, its axis of march the Staunton-Parkersburg Turnpike, advanced from Cheat Mountain and occupied in succession Camp Allegheny, Monteray, McDowell, and Shenandoah Mountain. Retreating before the incoming Federals, Confederate Brig. Gen. Edward Johnson pulled back to Westview, six miles south of Staunton. Union soldiers of Brig. Gen. Jacob D. Cox's District of Kanawha threatened the East Tennessee & Virginia Railroad.
The Federals by mid-May, although ousted from Pearisburg, held Mercer County and braced for a lunge at the railroad. Confederate Brig. Gen. Humphrey Marshall arrived from Abingdon, Virginia, with the Army of East Kentucky. Boldly seizing the initiative, Marshall bested Cox's two brigades during three days of fighting, May 15 - 17, in Mercer County centering on Princeton Courthouse.
Breaking contact with the Confederates on the night of the 17 - 18, Cox withdrew 20 miles to Camp Flat Top. Col. George Crook, commanding Cox's 3rd brigade, marched via the James and Kanawha Turnpike and occupied Lewisburg, where on May 23 he defeated Brig. Gen. N.P. Banks' division at Winchester (March 25) and driven it across the Pototmac, Crook evacuated Lewisburg and pulled back to Meadow Bluff.