Early in February the infantry columns of Grant and the gunboats of Commodore Foote commenced the ascent of the Tennessee River. The immediate object of assault was Fort Henry, an imperfectly constructed fortification, on the east bank of the river, near the dividing line of Kentucky and Tennessee. After a signal display of gallantry by its commander, General Tilghman, the fort was surrendered, the main body of the forces defending it having been previously sent to Fort Donelson, the principal defense of the Cumberland River. The capture of Fort Henry opened the Tennessee River, penetrating the States of Tennessee and Alabama, and navigable for steamers for more than two hundred miles, to the unchecked advance of the enemy. General Grant promptly advanced to attack Fort Donelson. After a series of bloody engagements and a siege of several days, Fort Donelson was surrendered, with the garrison of more than nine thousand men. This result was indeed a heavy blow to the Confederacy, and produced a most alarming crisis in the military affairs of the Western Department. General Johnston was near Nashville, with the force which had lately held Bowling Green, the latter place having been evacuated during the progress of the fight at Fort Donelson. Nashville was immediately evacuated, and the remnant of General Johnston's army retreated southward, first to Murfreesboro', Tennessee, and afterwards crossed the Tennessee, at Decatur, Alabama. In January, General Beauregard had been transferred from Virginia to Kentucky, and, at the time of the surrender of Nashville, was in command of the forces in the neighborhood of Columbus, Kentucky, which protected the passage of the Mississippi. The entire Confederate line of defense in Kentucky and Tennessee having been lost with the surrender of Forts Henry and Donelson, its various posts became untenable. In a subsequent portion of this narrative, we shall trace the results of the Confederate endeavor to establish a new line of defense in the West by a judicious and masterly combination of forces.