On 12 October 1861, became the first ironclad to enter combat, when she fought Union warships on the Mississippi during the Battle of the Head of Passes. She had been converted from a commercial vessel in New Orleans for river and coastal fighting. In February 1862, the larger joined the Confederate Navy, having been rebuilt at Norfolk. Constructed on the hull of , "Virginia" originally was a conventional warship made of wood, but she was converted into an iron-covered casemate ironclad gunship, when she entered the Confederate Navy. By this time, the Union had completed seven ironclad gunboats of the , and was about to complete , an innovative design proposed by the Swedish inventor John Ericsson. The Union was also building a large armored frigate, , and the smaller .