Reporting in person at the War Department on the morning of July 10, I was directed to report to Major General H. W. Halleck, U. S. Army, who assigned me to duty in the Department of Washington, to command a reserve camp to be located on or near Pinery Branch Creek, bout midway between Washington and Fort Stevens on the north. I company with Lieutenant Colonel B. S. Alexander, U. S. Engineers, I at once proceeded to examine the ground for the camp, also to make hasty examination of the fortifications on the north of Washington. Returning at 6 p. m., and receiving my final instructions from Major General C. C. Augur, commanding department, I proceeded to Piney Branch, where the Second Regiment District of Columbia Volunteers, Colonel Alexander, and the Ninth Regiment Veteran Reserve Corps, Lieutenant-Colonel Johnston, Captain Gibbs' (Ohio) battery, and Captain Bradbury's (Maine) battery had already reported.
Monday morning discovered the fact that the only troops on the north of Washington were the small garrisons in the forts, small detachments of cavalry in the front, and the troops above mentioned. Hearing of the near approach of the enemy, the idea of a reserve camp was at once abandoned and every man was brought forward and posted in the rifle-pits to the best advantage, and as strong a skirmish line as was prudent established. During the morning several additional regiments of the Veteran Reserve Corps and several detachments of dismounted cavalry reported for duty. They were posted din the rifle-pits on either, side of the main road leading to Silver Spring. Captain Berry, of the Eighth Illinois Cavalry, being stationed with his company on the road leading from Silver Spring to Leesborough, dispatched a courier at 10 a. m. the 11th, informing me that the enemy was advancing in force on that road with infantry, artillery, and cavalry. At 12 m. a strong line of the enemy's skirmishers came in view, advancing upon our position. The picket line at this moment was composed of 100-days' men of One hundred and fiftieth Ohio, and a portion of the Twenty-fifth New York Cavalry (dismounted). Being satisfied that they could not contend favorably against the enemy's line, were ordered to fall back slowly, fighting, until they reached the rifle-pits. Fire was then opened at proper points upon our line, and the enemy was held in check until the dismounted of the Second Division of the Cavalry Corps, Army of the Potomac, 600 strong, commanded by Major George G. Briggs, Seventh Michigan Cavalry, were made ready to go out, drive the enemy back, and re-establish our picket-line. This was handsomely done about 1.30 p. m., the enemy's skirmishers being forced back, and our line well established at 1,100 yards in front of the works. The enemy not developing any force other than their skirmish line, affairs remained in this condition until evening. About 3 p. m. Major General H. G. Wright, U. S. Volunteers, commanding the Sixth Army Corps, reported to me at Fort Stevens, informing me that the advance of his corps would be up in a short time. I directed him to furnish a force 900 strong of this veteran corps for picket duty during the night, constant skirmishing being kept up between the lines until after dark on the 11th instant. At 9 p. m. Brigadier General M. C. Meigs, Quartermaster-General U. S. Army, reported at Fort Stevens with about 1,500 quartermaster employees, armed and equipped. They were at once ordered into position near Fort Slocum, placed on right and left in rifle-pits. At 10 p. m. Colonel Price reported with about 2,800 convalescents and men from