The main defenses of the Mississippi River consisted of two permanent forts, Fort Jackson and Fort St. Philip, along with numerous small auxiliary fortifications. The two forts were of masonry and brick construction, armed with heavy rifled guns as well as smoothbores and located on either river bank to command long stretches of the river and the surrounding flats. In addition, the Confederates had some improvised ironclads and gunboats, large and small, but these were outnumbered and outgunned by the Union Navy fleet.