Headquarters of the Army,
Plan del Rio, April 17, 1847.
The enemy's line of intrenchments and batteries will be attacked in front, and at the same time turned, early in the day, to-morrow, probably before ten o'clock a.m.
The second (Twiggs') division of regulars is already advanced within easy turning distance towards the enemy's left. That division has instructions to move forward before daylight to-morrow and take up a position across the national road in the enemy's rear, so as to cut off a retreat towards Xalapa. It may be reinforced to-day if unexpectedly attacked in force, by regiments, one or two taken from Shields' brigade of volunteers. If not, the two volunteer regiments will march for that purpose at daylight to-morrow morning, under Brigadier-General Shields, who will report to Brigadier-General Twiggs, on getting up with him, or the general-in-chief, if he be in advance.
The remaining regiment of that volunteer brigade will receive instructions in the course of this day.
The first division of regulars (Worth's) will follow the movement against the enemy's left at sunrise to-morrow morning.
As already arranged, Brigadier-General Pillow's brigade will march at six o'clock to-morrow morning along the route he has carefully reconnoitered, and stand ready as soon as he hears the report of arms on our right, or sooner if circumstances should favor him, to pierce the enemy's line of batteries at such point, the nearer the river the better, as he may select. Once in the rear of that line, he will turn to the right or left, or both, and attack the batteries in reverse; or, if abandoned, he will pursue the enemy with vigor until further orders.
Wall's field battery and the cavalry will be held in reserve on the national road, a little out of view and range of the enemy's batteries. They will take up that position at nine o'clock in the morning.
The enemy's batteries being carried or abandoned, all our divisions and corps will pursue with vigor.
This pursuit may be continued many miles, until stopped by darkness or fortified positions, towards Xalapa. Consequently the body of the army will not return to this encampment, but be followed to-morrow afternoon, or early the next morning, by the baggage trains of the several corps. For this purpose, the feebler officers and men of each corps will be left to guard its camp and effects, and to load up the latter in the wagons of the corps. A commander of the present encampment will be designated in the course of this day.
As soon as it shall be known that the enemy's works have been carried, or that the general pursuit has been commenced, one wagon for each regiment and one for the cavalry will follow the movement, to receive, under the direction of medical officers, the wounded and disabled, who will be brought back to this place for treatment in general hospital.