HEADQUARTERS DEFENSES SOUTH OF WASHINGTON,
September 15, 1862 - 10.30 p. m.

Captain IRWIN,

Acting Assistant Adjutant-General, Washington:

I have sent a strong force of cavalry, with artillery, toward Leesburg, and from there across to the Bull Run Mountain. My intention was to advance General Stoneman's division to Fairfax Court-House, and one of General Sigel's divisions toward Leesburg. Now I am at a loss to find troops. I cannot take General Grover, as it will entirely uncover our left flank; besides, his pickets extend some 8 miles, and it will take too long to relieve them. Sending these troops across the Potomac, and a division to Fairfax Court-House, will necessarily break the line of defense; but, as the latter would be directly in front of the position they now occupy, this would be no disadvantage. General Sigel's troops are all toward the right. I do not see how I can advance a division without more troops from the other side.

S. P. HEINTZELMAN,

Major-General.

[P. S.] - General Stoneman's troops will come at daylight to-morrow. He will report in person in the morning.

HEADQUARTERS DEFENSES OF WASHINGTON,
September 15, 1862 -11.30 p. m.

Major General S. P. HEINTZELMAN, Arlington:

Pending a reply from the general, to whom I send your telegram, received 11.15, please inform me whether it would not, in your opinion, be satisfactory to send one of Sigel's divisions forward, as you propose, and supply its place in the line by a brigade of four new regiments form Casey, having somewhat more than the same numerical strength. The whole of Casey's command, twelve regiments, is to concentrate on the Virginia side to-morrow. Please answer immediately.

RICH'D B. IRWIN,

Captain, Aide-de-Camp, and Actg. Asst. Adjt. General

HEADQUARTERS DEFENSES OF WASHINGTON,
September 15, 1862 - 11.50 p. m.

Major General S. P. HEINTZELMAN, Arlington:

General Banks decides to send Stoneman's command up the river on this side, as heretofore ordered, but to defer the advance toward Fairfax until more complete arrangements can be made. The surrender at Harper's Ferry may change affairs on both sides. In the mean time put all your troops in condition to advance at short notice, when ordered.

By command:

RICH'D B. IRWIN,

Captain, Aide-de-Camp, and Actg. Asst. Adjut. General

SPECIAL ORDERS, HDQRS. OF THE ARMY, ADJT. GEN'S OFFICE,

No. 242. Washington, September 15, 1862.

* * * * * * *

III. Brigadier General W. F. Barry, U. S. Volunteers, inspector of artillery.