The Union ironclads played an important role in the Mississippi and tributaries by providing tremendous fire upon Confederate forts , installations and vessels with relative impunity to enemy fire . They were not as heavily armored as the ocean @-@ going monitors of the Union , but they were adequate for their intended use . More Western Flotilla Union ironclads were sunk by torpedoes ( mines ) than by enemy fire , and the most damaging fire for the Union ironclads was from shore installations , not Confederate vessels .