HEADQUARTERS U. S. FORCES,
Port Hudson, La., April 9, 1864.

COLONEL: I have the honor to report that on the 7th instant, the telegraph line between this post and Baton Rouge having ceased to work, a repairer was sent out to repair the line, with an escort of 100 cavalry under the command of Captain Shaw, of the One hundred and eighteenth Illinois Mounted Infantry, and one gun, without caisson, from the Twenty-first New York Battery, in charge of Second Lieutenant Potts. This detachment proceeded about 8 miles from this post on the Baton Rouge road, when it was attacked by an overwhelming force of the rebel cavalry, and obliged to fall back, which was done in good order until the detachment was within 1 1/2 or 2 miles of the fortifications, when it was again suddenly attacked in flank by the rebels, who had sent a party in on the Springfield Landing road, driving in our cavalry outposts. In the melee which followed, the rebels succeeded in capturing the gun; most of the detachment escaped. Our loss is as follows: Cavalry, One hundred and eighteenth Illinois, 1 lieutenant and 1 enlisted man wounded, 6 enlisted men missing; Third Illinois, 3 enlisted men wounded, 3 enlisted men missing; total, 5 wounded (1 since died), 9 missing. Artillery, 7 enlisted men missing, 6 horses, 1 piece without caisson; aggregate loss, 5 wounded, 16 missing, 6 horses, 1 gun. I am of the opinion that the affair was as well conducted on our part by Captain Shaw as circumstances would permit; that our loss was small under the circumstances; that the result is one that was to be feared with so small a cavalry force as I now have, with a line of 28 miles of telegraph on this side of the river, and at least as much on the other side to maintain.

The force of the enemy is estimated at from 600 to 800 men in the affair of yesterday. Several of them were known to be shot in the action, but their loss is unknown. A strong force of infantry and artillery, with the little remaining cavalry available, was sent out to support the detachment with all possible dispatch, but was too late to do any good. A portion of my cavalry force had been employed on the west bank in protecting the construction of the line to the mouth of Red River.

If I am to maintain the telegraph line as it now is, an additional cavalry force will be indispensable. I would, however, respectfully recommend that the telegraph line from Port Hudson to Baton Rouge be transferred to the west bank of the river along the levee. The force of the enemy now on that side does not, I am informed, exceed 130 men, and in the present position of our forces in Western Louisiana can be probably dispersed. The new location of the line will bring it within reach of a steamer, enabling me to support the cavalry with infantry and artillery if necessary, without involving fatiguing marches. There is already a line on the other side of the river, which I presume I shall have to maintain.

It is desirable that the cavalry force at this post be increased if practicable. I am urging the preparation of another brigade of infantry for the field.

I am, colonel, respectfully, your obedient servant,

GEORGE L. ANDREWS,

Brigadier-General of Volunteers, Commanding.

Lieutenant Colonel R. B. IRWIN,

Assistant Adjutant-General.