Inset view from the The new naval and military map of the United States by John Calvin Smith. The Battle of CSS Merrimack and USS Monitor was the first duel between ironclad warships and signaled in a new era of naval warfare. the Merrimack (renamed CSS Virginia) virtually decimated a Union navy fleet off Newport News, Virginia before Union ironclad Monitor came to the rescue. The two vessels engaged in battle, but ultimately ended in a sort of draw. Later, the battle was interpreted as a victory for Monitor.