President Lincoln had declared a blockade of the Southern ports as soon as the war had started. The Federal Navy Yard at Norfolk was captured by the Confederates without resistance. The United States ships were only twelve in number at the beginning of the war, but others were quickly constructed. The Confederates hoped to keep the James River open at all times. They needed ships badly, having had no navy to draw upon for ships. When the Federal employees had abandoned the Norfolk Navy Yard, they had sunk a wooden frigate called the "Merrimac." Governor Letcher of Virginia ordered that this ship be raised and be converted into an effective, usable frigate. Lieutenant John M. Brooke, John L. Porter, W. P. Williamson and others planned together for a converted ship. Finally, the hull of the old ship was covered with pine, oak and iron plates from the famous Tredegar Iron Works of Richmond. It was equipped with ten guns and an inexperienced crew under the ex-United States Naval Commander, Franklin Buchanan. This iron-clad vessel was renamed the "Virginia," and it traveled to Hampton Roads to attack the Federal fleet on March 8, 1862. When it first received gunfire from a Federal ship, the shots surprisingly glanced off its sides. The vessel moved very slowly. When at close range, it pierced the "Cumberland" with its iron ram causing it to sink. The next day, much to its surprise, it was matched by a Union ship, the "Monitor," designed by John Ericsson, which was ironclad, smaller, more agile and newly constructed throughout. The ships fired upon each other, but they could not inflict serious damage. The Battle of the "Monitor" and the "Virginia" (formerly "Merrimac") was a draw or indecisive from a victory point of view. However, it is important historically as the first battle of ironclad vessels in the United States. The "Virginia" was later blown up when the Confederates evacuated Norfolk. On March 23 of the same year, "Stonewall" Jackson became the aggressor and attacked a Union force at Kernstown, near Winchester. However, when one of his brigade became short of ammunition, he had to retreat southward. This battle was the beginning of Jackson's "Valley Campaign."