As early as the 2d of March Porter assembled at the mouth of the Red River a great fleet of nineteen ironclads, including fifteen of the heavier class and four of the lighter. The fleet carried 162 guns, of which 62 were of the higher calibres, from 80-pounder rifles up to 11-inch Dahlgrens, and the combined weight of projectiles was but little less than five tons.
On the 10th of March, A. J. Smith embarked his force at Vicksburg on an admirably organized fleet of nineteen river transports, controlled by a simple system of signals from the flagship _Clara Bell_. When, the next day, Smith joined Porter at the mouth of the Red River, six days were still left until the time when Banks had agreed to be at Alexandria with his army. Sherman's orders to Smith required him to make use of the interval by co-operating with the navy in an expedition up the Black and the Washita, for the destruction of Harrisonburg, but Porter had already done the work single-handed. Naturally supposing that Banks's troops were in march up the Teche toward the point of meeting, although they knew that Banks himself was still detained at New Orleans, Smith and Porter determined at once to take or turn Fort De Russy, and then to push on to Alexandria. On the morning of the 12th of March, the combined fleet entered the Red River. At the head of the Atchafalaya, Porter, with nine of the gunboats, turned off to the left and descended that stream as far as Simmesport, followed by the army transports, while Phelps, with the _Eastport_ and the remainder of the fleet, continued the ascent of the Red River, with a view of threatening Fort De Russy, and occupying the attention of its defenders until Smith could land and march across country to attack them.
On the morning of the 13th of March Smith landed, and toward nightfall took up the line of march for Fort De Russy, distant by land twenty-eight miles, although by the windings of the river nearly seventy. In his front, Smith found Scurry's brigade of Walker's division partly entrenched on Yellow Bayou; but Mower quickly brushed Scurry aside, and Walker, after observing the strength of his enemy, concentrated on the Bayou De Glaze, to avoid being shut up in the elbow at Marksville, as well as to get Mouton in support; and thus the way was open to Smith. On the afternoon of the 14th, Mower arrived before Fort De Russy, and just before nightfall the brigades of Lynch and Shaw swept over the parapet and forced a surrender, with a loss of 3 killed and 35 wounded. The captures included 25 officers and 292 men, and ten guns, of which two were 9-inch Dahlgrens from the spoils of the _Indianola_ and the _Harriet Lane_, once more restored to their first owners.