Main battery

Generally used only in the terms of naval warfare, the main battery is the primary weapon around which a ship was designed. "Battery" is in itself a common term in the military science of artillery. For example, the United States Navy battleship USS Washington had a main battery of nine 16 in 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 weapon. The term also refers to smaller ships, like heavy or light cruisers.

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, 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 used dual-purpose guns 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 missiles, replacing heavy naval artillery designs. An excellent example would be the Soviet/Russian Kirov class rocket cruisers. In the 1980s the four battleships of the United States Iowa class were fitted with Tomahawk and Harpoon missiles, their 16-inch guns were still retained.