When Gen. Henry W. Halleck was placed in command of the Department of Missouri, in November, 1861, he divided it into districts, giving to Gen. Ulysses S. Grant the District of Cairo, {75} which included Southern Illinois, the counties of Missouri south of Cape Girardeau, and all of Kentucky that lies west of Cumberland River. Where the Tennessee and the Cumberland enter Kentucky from the south they are about ten miles apart, and here the Confederates had erected two considerable works to command the rivers--Fort Henry on the east bank of the Tennessee, and Fort Donelson on the west bank of the Cumberland. They had also fortified the high bluffs at Columbus, on the Mississippi, twenty miles below the mouth of the Ohio, and Bowling Green, on the Big Barren. The general purpose was to establish a military frontier with a strong line of defence from the Alleghany Mountains to the Mississippi. [Illustration: THE BURNSIDE EXPEDITION CROSSING HATTERAS BAR.] [Illustration: ROANOKE ISLAND, N. C., AND CONFEDERATE FORTS.] A fleet of iron-clad gunboats had been prepared by the United States Government for service on the Western rivers, some of them being built new, while others were altered freight-boats. After a reconnoissance in force by Gen. C. F. Smith, General Grant asked Halleck's permission to capture Fort Henry, and, after considerable delay, received it on the 30th of January. That work was garrisoned by three thousand men under Gen. Lloyd Tilghman. Its position was strong, the ravines through which little tributaries reached the river being filled with slashed timber and rifle-pits, and swampy ground rendering approach from {76} the land side difficult. But the work itself was rather poorly built, bags of sand being largely used instead of a solid earth embankment.