John G. Nicolay, The Outbreak of Rebellion

This event both justified and sustained the movements of the West Virginia Unionists and the Government. If General McClellan had needed any further reasons for an active military interference, they were furnished by the fact that Porterfield began burning bridges on the Baltimore and Ohio Railroad. Realizing that delay was becoming dangerous, and prompted by directions from Washington, McClellan, on the 26th, ordered two regiments to cross the river at Wheeling, and two others at Parkersburg, and to simultaneously move forward by the branch railroads from each of these points to their junction at Grafton. Owing to the necessity of repairing burnt bridges, their progress was cautious and slow. This gave ample time for Porterfield to become fully informed of the movement; whereupon he retired with his small command, stores and spare arms, to Philippi, on a country road, about fifteen miles directly south of Grafton, hoping to find there a secure retreat about which to gather a sufficient force to return and more thoroughly cut, harass, or control, the railroad.

But the Union forces, being in superior numbers, and assisted with ready information by friendly local sentiment, gave the rebels little respite. General McClellan had forwarded additional regiments to Grafton, with Brigadier-General Morris, an educated West Point officer, to command; and he now adopted and completed an expedition already projected before his arrival by Colonel Kelly, who, with his West Virginia regiment, had a thorough knowledge of the country. Under pretence of an advance on Harper's Ferry, Colonel Kelly, at the head of about two regiments, started eastward by rail on the morning of June 2d; that evening a similar detachment under Colonel Dumont started westward;