In March, Johnston withdrew southward; and McClellan, his command now restricted to the “Army of the Potomac,” as he had baptized his splendid creation, was ready for the long-delayed advance. Lincoln, whose good sense when applied to warfare often, though not always, struck true, earnestly desired that Richmond should be approached by a direct southward movement, Washington being covered, while at the same time Richmond was threatened. But McClellan judged it better to proceed by the Chesapeake, landing at the end of the peninsula running up between the York and James rivers, and marching against Richmond from the east. Much could be said in favor of this route: troops and supplies could be carried by water to the neighborhood of Richmond without fatigue or danger. Yet the President yielded reluctantly, fearing danger to Washington, laying it down as fundamental that the capital must be protected by forty thousand men. The Peninsular campaign had a dramatic prelude. A necessary condition was a command of the waters, which was secured in early March by an event that startled the world. Among the many disadvantages under which the South labored in her struggle with the North was a painful lack, as compared with her opponent, of factories, machine-shops, ship-yards, and skilled labor; yet determination and ingenuity brought about several wonderful fighting contrivances, of which the most remarkable was the _Virginia_. The hull of the _Merrimac_, a frigate of thirty-five hundred tons and forty guns, one of the most formidable vessels of the old navy, partly burned and afterward sunk at the evacuation of Norfolk by the Federals in April, 1861, was raised, and found to be sound enough for further use. Good heads, among whom John M. Brooke, manager of the Tredegar Iron Works at Richmond, was prominent, fitted to the hull a casemate, or box, pierced for cannon, and heavily plated with iron--the first effective armored ship. There was a frank farewell to masts, sails, and other former appliances for motion and management. The winds were superseded by steam, applied for the first time in naval warfare, not as auxiliary, but as the sole motive-power. One appliance of the _Virginia_ was, however, not a new invention, but a revival of a fighting arm common in the days of Salamis and Actium--a ram, projecting from the prow like that of an ancient galley.[212] The craft was cumbrous, hard to steer, and provided with engines far too weak for her immense weight, but she had marvellous defensive power and was fast enough to approach and destroy any resisting sailing-ship. [Illustration: HAMPTON ROADS]