In the latter part of January, 1862, it became evident that General Johnson, with the inferior force at his disposal, could not hold his line in Kentucky. Crittenden, upon the right flank, had sustained a serious disaster at Mill Springs, near Somerset, and had been forced back across the Cumberland, which he had crossed to attack Thomas. In this battle General Zollicoffer was killed--his death was in itself an irreparable loss. Crittenden retreated first upon Monticello and subsequently to Gainesville in Tennessee. He lost his artillery and trains, and his troops could be relied on to oppose no effective resistance--for the time--to the farther advance of the enemy. The superiority of the latter in numbers had been not more marked than their superiority in arms and equipment. The fatigue and privation endured by Crittenden's men upon their retreat had contributed greatly to impair their efficiency. The expeditions against Forts Henry and Donelson were vigorously pressed, and scarcely had full confirmation arrived of the defeat of Crittenden, when we got the first rumors of the fall of Fort Henry. General Johnson had never been able to collect at all the points of defense in Kentucky, exclusive of Columbus, more than twenty-four thousand men. In this force were included sixty-days' men and all the minor garrisons. He had at Bowlinggreen in January and the first of February about ten thousand.
Buell had organized, during the period that the two armies lay inactive and confronting each other, fifty or sixty thousand men, and they were, at the time when General Johnson commenced his retreat, concentrated, mobilized, and ready to fall upon him. Therefore, even before it became evident that Donelson must fall, before the capture of Nashville was imminent, by an enemy moving from either flank, and before his line of retreat was endangered, but just so soon as Buell put his army in motion General Johnson evacuated Bowlinggreen. Then began the campaign, in which more than in any other of the war, was displayed the profoundest strategy, the most heroic decision, the highest order of generalship.
General Johnson had long foreseen the storm of difficulties which now assailed him. His resources were scanty and the emergency was terrible, but he did not despair of fighting through it to victory. Upon one flank of his line, he had sustained a crushing defeat, the forces protecting it had been driven off. Nashville might be taken by the victors. One of the forts protecting the great water lines which led right into the heart of his department, and away to the rear of his army, had been taken. If the other fell the fate of Nashville was sealed, but far worse, he would be inclosed at Bowlinggreen, should he remain there, between three armies each much stronger than his own. If he lingered around Nashville, he could not protect the city, but gave his enemy the opportunity of cutting him off completely from the only territory whence he could hope to obtain recruits, and of preventing his junction with the reinforcements which he had ordered to his assistance. He did not hesitate a moment.