Generally used only in the terms of naval warfare, the main battery is the primary weapon around which a ship was designed. "Battery

Artillery battery

In military organizations, an artillery battery is a unit of guns, mortars, rockets or missiles so grouped in order to facilitate better battlefield communication and command and control, as well as to provide dispersion for its constituent gunnery crews and their systems...

" is in itself a common term in the military science of artillery. For example, the United States Navy battleship USS Washington

USS Washington (BB-56)

USS Washington , the second of two battleships in the North Carolina class, was the third ship of the United States Navy named in honor of the 42nd state. Her keel was laid down on 14 June 1938 at the Philadelphia Naval Shipyard. Launched on 1 June 1940, Washington went through fitting-out before...

 had a main battery of nine 16 inches (406.4 mm) guns arranged in three turrets, two forward and one aft. The secondary battery was 5-inch dual purpose guns, meaning they could be fired against other ships or used as an anti-aircraft

Anti-aircraft warfare

NATO defines air defence as "all measures designed to nullify or reduce the effectiveness of hostile air action." They include ground and air based weapon systems, associated sensor systems, command and control arrangements and passive measures. It may be to protect naval, ground and air forces...

 weapon. The term also refers to smaller ships, like heavy

Heavy cruiser

The heavy cruiser was a type of cruiser, a naval warship designed for long range, high speed and an armament of naval guns roughly 203mm calibre . The heavy cruiser can be seen as a lineage of ship design from 1915 until 1945, although the term 'heavy cruiser' only came into formal use in 1930...

 or light cruiser

Light cruiser

A light cruiser is a type of small- or medium-sized warship. The term is a shortening of the phrase "light armored cruiser", describing a small ship that carried armor in the same way as an armored cruiser: a protective belt and deck...

s.

Often, ships had a primary battery for offensive purposes, and a secondary and sometimes even a tertiary battery for self-defense. An example of this was the German battleship Bismarck

German battleship Bismarck

Bismarck was the first of two s built for the German Kriegsmarine during World War II. Named after Chancellor Otto von Bismarck, the primary force behind the German unification in 1871, the ship was laid down at the Blohm & Voss shipyard in Hamburg in July 1936 and launched nearly three years later...

, which carried a primary battery of eight 15 inch (380mm) guns, along with a secondary battery of twelve 5.9 inch (150mm) guns for defense against destroyers and torpedo boats, as well as a tertiary battery of various anti-aircraft guns ranging in caliber from 4.1 inch (105mm) to 20mm guns. Many later ships during World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 used dual-purpose guns

Dual purpose gun

A dual purpose gun is a naval artillery mounting designed to engage both surface and air targets.-Description:Second World War-era capital ships had four classes of artillery: the heavy main battery, intended to engage opposing battleships and cruisers ; a secondary battery for use against enemy...

 to combine the secondary battery and the heavier guns of the tertiary batteries, in order to simplify the design.

Newer vessels are designed with anti-ship missile

Anti-ship missile

Anti-ship missiles are guided missiles that are designed for use against ships and large boats. Most anti-ship missiles are of the sea-skimming type, many use a combination of inertial guidance and radar homing...

s, replacing heavy naval artillery designs. An excellent example would be the Soviet/Russian Kirov class

Kirov class battlecruiser

The Kirov-class battlecruiser is a class of nuclear-powered military ships of the Russian Navy, the largest and heaviest surface combatant warships currently in active operation in the world. The Russian designation is heavy nuclear-powered guided missile cruiser...

 rocket cruisers. In the 1980s the four battleships of the United States Iowa class were fitted with Tomahawk

BGM-109 Tomahawk

The Tomahawk is a long-range, all-weather, subsonic cruise missile. Introduced by General Dynamics in the 1970s, it was designed as a medium- to long-range, low-altitude missile that could be launched from a surface platform. It has been improved several times and, by way of corporate divestitures...

 and Harpoon

Harpoon

A harpoon is a long spear-like instrument used in fishing to catch fish or large marine mammals such as whales. It accomplishes this task by impaling the target animal, allowing the fishermen to use a rope or chain attached to the butt of the projectile to catch the animal...

 missiles, but their 16-inch guns were still retained.