The main batteries in 20th century battleships tended to be powered gun turrets which could swivel 180 degrees or more to establish wider firing arcs around the entire vessel. Although this could allow at least some of the main guns to be focused directly forward or aft, battleships still relied on broadsides for maximum firepower, as structures such as the bridge tower in the middle of a battleship would prevent guns in the aft portion of the ship from firing forward, and vice versa. Additionally, directing the guns to the port or starboard side projected the massive muzzle blast out over the ocean, while firing the guns too close to the deck could cause damage to the ship.