Even Kaiyo, which had been reputedly the sturdiest ship until then, was made of wood, so its inferiority in terms of defensibility was undeniable even with its superiority in weight and number of equipped cannons; thus ENOMOTO, much concerned about this situation, carried out an uncommon military operation to seize Kotetsu in a surprise attack.
当時最新最強と謳われた開陽でさえ木造艦であり、砲数・トン数では勝るものの防備性の劣勢は否めず、これを大いに憂慮した榎本は同艦奇襲・奪取の奇策を実行に移す。