 Through the remainder of the war , ironclads saw action in the Union 's attacks on Confederate ports . Seven Union monitors , including USS <unk> , as well as two other ironclads , the ironclad frigate New <unk> and a light @-@ draft USS <unk> , participated in the failed attack on Charleston ; one was sunk . Two small ironclads , CSS <unk> State and CSS <unk> participated in the defence of the harbor . For the later attack at Mobile Bay , the Union assembled four monitors as well as 11 wooden ships , facing the CSS Tennessee , the Confederacy 's most powerful ironclad and the gunboats CSS Morgan , CSS Gaines , CSS Selma . 
