Capital ship

The capital ships of a navy are its most important warships; they are generally the larger ships when compared to other warships in their respective fleet. A capital ship is generally a leading or a primary ship in a naval fleet.

William S. Lind, in the book America Can Win (p. 90), defines a capital ship as follows: "These characteristics define a capital ship: if the capital ships are beaten, the navy is beaten. But if the rest of the navy is beaten, the capital ships can still operate. Another characteristic that defines capital ships is that their main opponent is each other."

There is usually no formal criterion for the classification, but it is a useful concept in naval strategy; for example, it permits comparisons between relative naval strengths in a theatre of operations without the need for considering specific details of tonnage or gun diameters.

A notable example of this is the Mahanian doctrine, which was applied in the planning of the defence of Singapore in World War II, where the Royal Navy had to decide the allocation of its battleships and battlecruisers between the Atlantic and Pacific theatres. The war in Europe was primarily a land war; consequently, Germany's surface fleet was small, and the escort ships used in the Battle of the Atlantic were mostly destroyers and destroyer escorts to counter the U-boat threat.

The Mahanian doctrine was also applied by the Imperial Japanese Navy, leading to its preventive move to attack Pearl Harbor and the battleships of the U.S. Pacific Fleet. The naval nature of the Pacific Theater of Operations, more commonly referred to as the Pacific War, necessitated the United States Navy to deploy its battleships and aircraft carriers in the Pacific.

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