When six-inch secondaries make sense

Four-inch Royal Navy secondary batteries suited destroyers and torpedo boats. Six-inch guns became useful when a battlecruiser might need to fight cruisers while its main battery engaged heavier ships. British battleships generally retained four-inch weapons until the Iron Duke class because their main guns were expected to deal with anything larger than torpedo craft. At Jutland, Robert Arbuthnot's First Cruiser Squadron crossed in front of the British battlecruiser force and placed itself between the Grand Fleet and High Seas Fleet. Its smoke and gunfire obstructed the Grand Fleet's view, while the German fleet's main guns pummelled the cruisers. Their destruction shows why ships within capital-ship gun range could be handled without a six-inch battleship battery. Calibre choice therefore reveals whether a navy expected light attackers alone or a heavier cruiser threat.