Monitor and Merrimack fought a famous naval battle in the American Civil War (1861-1865). The two ships were called ironclads because they had been covered with iron. The battle, which ended with little damage to either the Union's Monitor or the Confederacy's Merrimack, focused worldwide attention on the importance of armor-plated ships. It was also the first sea battle in which the opposing ships were maneuvered entirely under steam power.