The St. Louis class "semi-armored cruisers" of the early 1900s employed an interesting weight-saving measure - they omitted the main armament! Amidships they had twelve 6" guns in armored casemates, a fairly typical secondary battery for an armored cruiser, but fore and aft, rather than twin 8" or 10" turrets, there were just single 6" guns, completely unprotected.