Ironclad warships were crucial, perhaps decisive, in the North's victory over the South in the American Civil War. Partial ironclads appeared early on the western rivers and spearheaded Union general Ulysses Grant's victories in 1862. River and coastal ironclads (ultimately, mostly Monitors) dominated the war against the South in attacks from the sea, and in decisive support of land operations. Most memorable of the combats was the duel between the Monitor and Virginia (better known as the Merrimack). The Virginia sailed on March 8, 1862, for its trial run. Defying concentrated fire of ship and shore batteries, it sank two ships of the Union's wooden blockading fleet before retiring with the ebbing tide. In this dramatic moment John Ericsson's Monitor arrived from New York during the middle of the night. Displacing fewer than 1,000 tons, the Monitor had a boxlike iron hull supporting an iron-plated wooden raft on which revolved the turret. The 172-foot-long vessel had little freeboard except for the thickly armoured rotating turret within which were mounted two 11-inch smoothbores.
The Monitor had many deficiencies. Not really a seagoing warship, it had nearly sunk on its voyage down from New York and did sink on its next sea voyage. Yet it proved the equal of its rival in their duel on March 9. The battle ended in a draw with neither ship seriously injured, but the repercussions of this first duel between completely ironclad warships swept the world.
