From the opening days of the Civil War, one of the Union's strategies in its efforts to defeat the rebelling southern states was to blockade their ports. Compared to the Union, relatively little was manufactured in the Confederacy―either consumer goods or, more important, war materials―and it was believed that a blockade could strangle the South into submission. But the Confederacy had 3,500 miles of coastline and, at the start of the war, the Union had only 36 ships to patrol them. 　　Even so, the Confederate government knew that the Union could and would construct additional warships and that in time all its ports could be sealed. To counter this, the Confederacy decided to take a radical step―to construct an ironclad vessel that would be impervious to Union gunfire. In doing so, the South was taking a gamble because, though the British and French navies had already launched experimental armor-plated warships, none had yet been tested in battle. 　　Lacking time as well as true ship-building capabilities, rather than construct an entirely new ship, in July, 1861, the Confederacy began placing armor-plating on the hull of an abandoned U.S. Navy frigate, the steam-powered US.S. Merrimack. Rechristened the C.S.S. Virginia, the ship carried ten guns and an iron ram designed to stave in the wooden hulls of Union warships. 　　Until then, Union Secretary of the Navy Gideon Welles had considered ironclads too radical an idea, and preferred to concentrate on building standard wooden warships. But when news of the Virginia reached Washington, the fear it engendered forced him to rethink his decision. In October, 1861, the Union began construction of its own ironclad―the US.S. Monitor―which would revolutionize naval warfare. 　　Designed by John Ericson, a Swede who had already made substantial contributions to marine engineering, the Monitor looked like no other ship afloat. With a wooden hull covered with iron plating, the ship had a flat deck with perpendicular sides that went below the waterline and protected the propeller and other important machinery. Even more innovative, the ship had a round, revolving turret that carried two large guns. Begun three months after work started on the conversion of the Virginia, the Monitor was nevertheless launched in January, 1862, two weeks before the Confederacy launched its ironclad. 　　On March 8th, now completely fitted, the Virginia left the port of Norfolk, Virginia, on what was expected to be a test run. However, steaming into Hampton Roads, Virginia, the Confederate ship found no fewer than five Union ships at the mouth of the James River―the St. Lawrence, Congress, Cumberland, Minnesota, and Roanoke. The first three of these were already obsolete sailing ships, but the others were new steam frigates, the pride of the Union navy. 　　Attacking the Cumberland first, the Virginia sent several shells into her side before ramming her hull and sinking her. Turning next to the Congress, the southern ironclad sent broadsides into her until fires started by the shots reached her powder magazine and she blew up. At last, after driving the Minnesota aground, the Virginia steamed off, planning to finish off the other ships the next day. In just a few hours, she had sunk two ships, disabled a third, and killed 240 Union sailors, including the captain of the Congress―more naval casualties than on any other day of the war. Although she had lost two of her crew, her ram, and two of her guns and sustained other damage, none of the nearly 100 shots that hit her had pierced her armor. 　　The Monitor, however, was already en route from the Brooklyn Navy Yard, and the next morning, March 9th, the two ironclads met each other for the first―and only―time. For nearly four hours the ships pounded at each other, but despite some damage done on both sides, neither ship could penetrate the armor-plating of its enemy. When a shot from the Virginia hit the Monitor's pilot house, wounding her captain and forcing her to withdraw temporarily, the Confederate ship steamed back to Norfolk.    Although both sides claimed victory, the battle was actually a draw. Its immediate significance was that, by forcing the withdrawal of the Virginia, it strengthened the Union blockade, enabling the North to continue its ultimately successful stranglehold on the South. Even more important, it was a turning point in the history of naval warfare. Although neither ship ever fought again, the brief engagement of the Monitor and Virginia made every navy in the world obsolete, and, in time spelled the end of wooden fighting ships forever.