The capture of Island No. 10 formed part of the effort to open the great rivers of the Confederacy to Federal control. Pope's Army of the Mississippi, assisted by a naval task force under Commo. Andrew H. Foote, brought more than 20,000 Federal troops and a fleet that included six gunboats, eleven mortar boats, and supporting tenders and transports against Confederate defenses first commanded by Maj. Gen. John P. McCown and later by Brig. Gen. L.M. Walker and Brig. Gen. William W. Mackall. After the fall of Forts Henry and Donelson, Lt. Gen. Polk evacuated Columbus, Kentucky, and strengthened New Madrid, Missouri, and Island No. 10. Pope marched from New Commerce to invest New Madrid, and McCown evacuated that town on March 15, sending most of his force to Fort Pillow while guns and artillerymen reinforced the island. To make a crossing possible, Federal engineers cut a passage through Bayou St. John for light-draft vessels, and by April 1 it was in use. Federal naval units began daily bombardment about March 15, while the Confederate defenders struggled with incomplete works, sickness, and severe flooding that damaged ammunition storage and helped force the abandonment of Battery No. 1 on April 2, when a landing party from USS Benton spiked its guns. On April 4 and 5, the Carondelet and then the Pittsburg ran past the island, and on April 7 they moved downstream, attacking and silencing Confederate batteries as far as Tiptonville. Anticipating Pope's crossing, Mackall gathered about 2,500 troops west of the island, but Pope ferried troops to Watson's Landing and advanced toward Tiptonville, where the two forces met north of the town at daylight on April 8 and Mackall's command was defeated and reported at about 2,000. The remaining defenders on the island, facing capture, tried to escape by boat across the flooded river during a snowstorm, while the floating battery was scuttled and later captured on the Missouri shore; about 500 escaped, mostly from the 12th Arkansas Infantry, and about 500 more were captured when Federal naval forces overran the island.