armored fighting vehicles. Anti-aircraft artillery: Guns, usually mobile, designed for attacking aircraft by land and/or at sea. Some guns were suitable for the dual roles of anti-aircraft and anti-tank warfare. Rocket artillery: Launches rockets or missiles, instead of shot or shell. Railway gun: Large-caliber weapons that are mounted on, transported by and fired from specially-designed railway wagons. Naval artillery: Guns mounted on warships to be used either against other naval vessels or to bombard coastal targets in support of ground forces. The crowning achievement of naval artillery was the battleship, but the advent of air power and missiles have rendered this type of artillery largely obsolete. They are typically longer-barreled, low-trajectory, high-velocity weapons designed primarily for a direct-fire role. Coastal artillery: Fixed-position weapons dedicated to defense of a particular location, usually a coast (for example, the Atlantic Wall in World War II) or harbor. Not needing to be mobile, coastal artillery used to be much larger than equivalent field artillery pieces, giving them longer range and more destructive power. Modern coastal artillery (for example, Russia's "Bereg" system) is often self-propelled, (allowing it to avoid counter-battery fire) and fully integrated, meaning that each battery has all of the support systems that it requires (maintenance, targeting radar, etc.) organic to its unit. Aircraft artillery: Large-caliber guns mounted on attack aircraft, this is typically found on slow-flying gunships. Nuclear artillery: Artillery which fires nuclear shells. Modern field artillery can also be split into two other subcategories: towed and self-propelled. As the name suggests, towed artillery has a prime mover, usually an artillery tractor or truck, to move the piece, crew, and ammunition around. Towed artillery is in some cases equipped with an APU for small displacements. Self-propelled artillery is permanently mounted on a carriage or vehicle with room for the crew and ammunition and is thus capable of moving quickly from one firing position to another, both to support the fluid nature of modern combat and to avoid counter-battery fire. It includes mortar carrier vehicles, many of which allow the mortar to be removed from the vehicle and be used dismounted, potentially in terrain in which the vehicle cannot navigate, or in order to avoid detection. Organizational types At the beginning of the modern artillery period, the late 19th century, many armies had three main types of artillery, in some case they were sub-branches within the artillery branch in others they were separate