I now faced about, my rear being menaced by the demonstrations of the enemy, and threw out about 60 cavalrymen beyond Sangster's Station, to picket and patrol from there to the right as far as Fairview, to the front to Fairfax Station, and to the left as far as Centreville; also pushed forward from this position, upon every approach leading to it, infantry detachments of from one to four companies, supported by four pieces of artillery.
Thus I have formed a complete chain of posts around Union Mills, was in communication with Fairfax Station, and had caused Colonel Wyndham to cover the direct approaches from the Occoquan to the same. These dispositions left only actually in my hands a force of one and a half regiments of infantry and a six-gun battery. One-half regiment had to serve as permanent support to the artillery, when the regiment (Thirty-ninth New York Volunteers, 400 men) should be used as reserve, ready to be thrown to the point of danger.
I then received General Stoughton's order to move, with two regiments and a battery, to Fairfax Station. It was about 2 a.m., December 29; the moon had gone down, and I knew the artillery could not be moved over the almost impassable roads at night; and, in addition, I was entirely ignorant of the topography of Fairfax Station, which all combined with my experience about night marches and maneuvers with young troops, on bad roads, in a country much cut up (tenain coupe), the enemy's position and movements a mystery, decided me not to move before daylight, but ordered increased vigilance and more patrolling with Fairfax Station.
With earliest dawn of the morning I marched with my one and a half regiments and battery to Fairfax Station, where I found arrived there four regiments of infantry and four pieces of artillery. The enemy had cut the telegraph wire and slightly destroyed the railroad track, both of which I repaired with my pioneer corps, and returned at 3 p.m. to this place. Having not hear yet where the enemy had gone to, being traced only to Vienna, and not knowing if he might not pass through Centreville, and via Gainesville, or still nearer me, to Warrenton, or out of our lines, I strengthened the forces holding my right flank with those from the left, which latter was apparently out of danger, and placed abatis in the approaches.
In this position I have remained until 9 a.m. to-day, December 30, holding my brigade in constant readiness and state of defense-offensive I could not be, having no cavalry. My patrols to Centreville have returned, reporting no enemy there, upon which I send the regiments back to camp, keeping, though, my 7 mounted orderlies and a few mounted artillerymen scouting on my right flank.
My men are greatly fatigued. My daily detail for guard and outpost duty is so large that they are on duty every second or third day. A great deal of sickness prevails, and the regiments average no more than 400 for duty. They have to do cavalry duty for the want of that arm, and I now urgently and earnestly beg that a regiment of infantry be ordered to replace the Twenty-sixth Michigan Volunteers, ordered away from here, and that at least a little cavalry re-enforce me, both for the purpose to preserve the health of my brigade (troubled with small-pox and measles) and to execute the duty laid upon me for the good of the country.
I have the honor to be, sir, your, respectfully,
F. G. D'UTASSY,
Colonel, Commanding Brigade.
Captain R. N. SCOTT,
Acting Assistant Adjutant-General.