"You have Fort Donelson safe, unless Grant shall be overwhelmed from outside; to prevent which latter will, I think, require all the vigilance, energy, and skill of yourself and Buell, acting in full co-operation. Columbus will not get at Grant, but the force from Bowling Green will. They hold the railroad from Bowling Green to within a few miles of Fort Donelson, with the bridge at Clarksville undisturbed. It is unsafe to rely that they will not dare to expose Nashville to Buell. A small part of their force can retire slowly towards Nashville, breaking up the railroad as they go, and keep Buell out of that city twenty days. Meantime, Nashville will be abundantly defended by forces from all south and perhaps from here at Manassas. Could not a cavalry force from General Thomas on the upper Cumberland dash across, almost unresisted, and cut the railroad at or near Knoxville, Tennessee? In the midst of a bombardment at Fort Donelson, why could not a gunboat run up and destroy the bridge at Clarksville? Our success or failure at Fort Donelson is vastly important, and I beg you to put your soul in the effort. I send a copy of this to Buell." Imagine his sensations when he received a reply from General Halleck: "Make Buell, Grant, and Pope major-generals of volunteers and give me command in the West. I ask this in return for Fort Henry and Donelson." The President realized the situation, made the promotions, consolidated the different departments west of the Blue Ridge Mountains, placed Halleck in command, and directed him to take advantage of "the golden opportunity;" but the latter was too deliberate, and it required only a brief experience to demonstrate that he was unfit to command troops in the field. He was called to Washington, placed at the head-quarters of the army to succeed General McClellan, and Grant was left in command of the army in Tennessee, where he undertook the task of opening the Mississippi in his own way, having the full confidence of the President.