Yet when the war broke out he felt that he must choose the national cause. In January, 1862, he was sent in charge of a squadron to secure the Mississippi River for the Union. He was to capture Fort Jackson and Fort St. Philip which defended New Orleans, then take the city, and afterwards sail up the river, subjecting the forts along the banks. He was in charge of the largest and best-equipped fleet that had ever been led by an American commander. It consisted of forty-eight vessels. An army of fifteen thousand soldiers under General Butler was sent to aid in the capture of New Orleans. Below the forts commanding the city, was a barricade of old vessels and logs fastened together with iron chains; above these was the Confederate fleet of fifteen vessels. For a week Captain Farragut’s mortar boats rained shells on the forts, then his gunboats broke the barricade. At four o’clock on the morning of April the twenty-fourth, his squadron passed the forts which had held back the British in 1815. Then they engaged in a desperate battle with the little Confederate fleet. Every vessel of it was captured or wrecked. Four days later the besieged forts surrendered, and on the first of May the Union troops under Butler took possession of New Orleans. Farragut was ordered to “pass or attack and capture” the Confederate forts between New Orleans and Memphis. He accordingly went to Vicksburg, but his expedition failed for lack of land-forces to support the attack. July 4, 1863, Vicksburg was taken by General Grant, and a few days later, Port Hudson was surrendered. This gave the Union forces entire control of the river. For his valiant and efficient service, Farragut was rewarded in 1862 with the rank of rear-admiral, created for his benefit. Thus he was the first admiral in the United States navy. Later he was made vice-admiral, and in 1866 he became admiral, each of the three ranks being created in his honor. While Farragut’s squadron was striving to gain control of the Mississippi, a battle took place on the Atlantic coast which marked the beginning of a new era in naval warfare, the end of wooden war-ships and the use of iron vessels. The Confederates captured a United States vessel, the Merrimac, removed its masts, covered it with iron, and fitted it with an iron prow. This iron-clad vessel attacked and destroyed several Union vessels. It was attacked by the Monitor, an iron-covered vessel designed by Captain John Ericsson and commanded by Lieutenant Worden. It carried larger guns than had ever before been used on a vessel. A fierce battle was fought in which neither of the iron-clads was seriously injured, and the Merrimac finally withdrew.