British zigzagging and Japanese long-range torpedo attacks

A long-range torpedo salvo depended on the target maintaining a predictable course. Some American opponents helped Japanese attacks succeed because they underestimated the Long Lance's range. British wartime doctrine required routine zigzagging, with restricted circumstances in which ships could remain on a steady course. That practice came from First World War experience with submarines, rather than knowledge of Japan's torpedo performance. A precaution developed against one threat could therefore disrupt an attack planned around another.