While I was absent on the expedition to Trevillian, the movement of the Army of the Potomac across the James River was effected, and Wilson, whom I had left behind for the purpose, was engaged in the duty of covering its front and rear.  Late on the night of June 12 he, with Chapman’s brigade, crossed the Chickahominy at Long Bridge, in advance of the Fifth Corps, and by 7 o’clock next morning had driven the enemy’s pickets up to White Oak bridge, where he waited for our infantry.  When that came up, he pushed on as far as Riddle’s Shop, but late that evening the Confederate infantry forced him to withdraw to St. Mary’s Church; for early in the morning General Lee had discovered the movement of our army, and promptly threw this column of infantry south of the Chickahominy to White Oak Swamp, with the design of covering Richmond.  From St. Mary’s Church Wilson guarded all the roads toward White Oak Swamp and Riddle’s Shop, McIntosh’s brigade joining him on the 14th, by way of Long Bridge, as the rear of the Army of the Potomac passed the Chickahominy.  In the performance of this duty Wilson did not have to fight any engagement of magnitude, for the bulk of the enemy’s cavalry had followed me to Trevillian.  During the 15th and 16th Wilson drew his troops in toward the James River, and next day crossed it on the pontoon-bridge and camped on the Blackwater, near Mt.  Sinai Church.  Here he remained till the 22d of June—­the same day I reached the White House with Gregg and Torbert—­when, under orders from General Meade, he set out to cut the enemy’s communications to the south and southwest of Petersburg.

His instructions implied that the breaking up of the Petersburg and Lynchburg, and Richmond and Danville railroads at Burkeville was the most important part of his mission, and that when the work of destruction began, it should be continued till he was driven off by the enemy.  Wilson’s force consisted of about 5,500 men, General A. V. Kautz, with the cavalry of the Army of the James, having joined him for the expedition.  In moving out Wilson crossed the Weldon road near Ream’s Station, first destroying it effectually at that point.  About fourteen miles west of Petersburg he struck the Southside railroad, and broke it up clear to Burkeville, a distance of thirty miles.  Having destroyed everything at Burkeville Junction, he moved along the Danville road to Staunton River, completely wrecking about thirty miles of that line also.  At Staunton River he found the railroad bridge strongly guarded, and seeing that he could not burn it, he began his return march that night, and reached Nottoway River, some thirty miles south of Petersburg, at noon of the next day—­the 28th.