His instructions from his brigade commander were that the holding of Charlestown itself was of no more importance than as though it was an open plain, but to be vigilant in scouting the country, watching the movements of the enemy in his front, to engage and whip any force that came within his reach that was not too strong for him, and if attacked by superior numbers to retire. From about the middle of September there appears to have been a force of rebels in that vicinity, which for some time were believed to be small, under the command of Major White. About the 1st of October it was rumored that an advance of a part of Lee's army in that direction might be expected, and that unusual vigilance was necessary. On the 7th of October he was informed by Colonel Wells, commanding brigade, that Imboden was said to be preparing to make a said on the railroad between Martinsburg and Harper's Ferry.

On the 13th of October he was directed to send a scouting party to Berryville, and one, consisting of 10 men, to follow the summit of Blue Ridge toward Front Royal. On the same day he informed Colonel Wells that he sent a force to Berryville, which drove in the enemy's pickets (supposed to be of White's battalion), but being too small to make an attack, returned; and that they could hear of no force approaching up the valley; and that the scout ordered to Blue Ridge had returned, being unable to proceed on that road; and he asked if they should endeavor to go forward by any other route. On the 14th it also appears that he had his wagons packed, and all preparations made to fall back to Harper's Ferry, but received an order from General Sullivan to wait till he was attacked. During the day he sent word to Colonel Wells that he had scouted every road leading from Charlestown, had found a force at Berryville, supposed to be White's, and a small force at Smithfield, but had gained no information of any heavy force in the valley. That he was informed that it was the intention to annoy his pickets that night; therefore he had increased their numbers, and would advance his posts on some of the roads, and have a company of men under arms to re-enforce any point that might be attacked. On the 15th he was informed by Colonel Wells that it was reported in Harper's Ferry that Imboden was at Berryville with "something of a force," and that a part of it was being sent around between Charlestown and the river, and that the matter should be looked into. Colonel Wells closed his communication by saying that the alarm about an approach up the valley seemed to have been without foundation, and that Colonel Simpson could resume the even tenor of his way at Charlestown the same as before. On the same day Colonel Wells further informed him that he had sent a detachment of cavalry on the road from Martinsburg to Winchester and Berryville, with orders to convey any information they might obtain to Charlestown.

On the 17th Colonel Simpson informed Colonel Wells that a detachment of cavalry came into Charlestown the night before, being unable to reach Berryville on account of White's occupation of it. That an officer of Cole's battalion had arrived, having been wounded in a skirmish, and that he represented that no other force was in the valley but Imboden's; and further that he had captured one of White's men, who informed him that White's battalion, consisting of 150 cavalry and 80 dismounted as infantry, had been at Berryville, had reconnoitered the position at Charlestown, and had found it too strong for them; and that White had moved away, and Imboden