A ship covered with iron plates and used in the Civil War, in the famous Merrimac vs. Monitor first ever naval battles between the ironclads in 1862. They revolutionized naval warfare.
Military leadership in order of importance and decision-making responsibilities usually prioritized from the Commander-in-Chief(president), General of the Army, Lt. General, Major General, Brigadier General general, Colonel, Major, Captain, Lieutenant, 1st Sergeant, Corporal, Private.