A second defect in this scheme of defense was that the line thus formed was traversed by two rivers, the Tennessee and the Cumberland, both practically navigable by steamboats. It was obvious to ordinary common-sense that should both or either of these rivers at any time fall under control of the enemy, with his multitudinous gunboats and other river craft which could easily be made to carry guns, the western half of the Confederate force must be completely and at once cut off from all but a very roundabout and slow communication with its allies on the east. Here was a danger which must have presented itself obtrusively to the minds of those who formed and ordered this military arrangement. It is difficult for a military critic in this later day to understand or to conceive upon what principle of scientific warfare such a line was accepted as even tolerably judicious. Its adoption seems in fact to have been determined more by political than by military considerations. In order to meet the difficulty the Confederates created the two great fortresses--Henry and Donelson--to defend the rivers. These forts were curiously misplaced. They were located one upon the one river, and the other upon the other, at a point near the dividing line between Kentucky and Tennessee. At that point the two rivers run within eleven miles of each other. But a little farther down the streams--that is to say a little farther north--their course brings them within three miles of each other. Here obviously on all accounts was the point at which the defensive works should have been constructed. In that case the two forts would have been within easy supporting distance of each other and neither could have been assailed from the rear. Moreover, we have the authority of no less eminent an engineer than General Beauregard for saying that the ground at this point is well fitted by its natural conformation for purposes of defense, while at the point actually selected for the two fortresses it is peculiarly lacking in that advantage. But the more defensible position was in Kentucky and purely political considerations had weight in determining the choice of the less advantageous point of defense in Tennessee. The defective character of this line of defense and the mistake underlying its acceptance were strongly emphasized after the overthrow of Zollicoffer at Mill Springs and the pushing forward of General Thomas's forces to more southerly points. This movement placed a threatening force on the right flank of the Confederate line of defense. Nevertheless, the Confederate War Department clung to its mistaken policy. It lived at that time in a fool's paradise in which facts counted for little in comparison with theories, and in which optimism was expected to serve the purpose of guns and brigades and defensive works.