On February 1, 2018, The Ministry of Defence’s Maritime Staff Office, revealed that seven of the service’s 82 m Oyashio-class submarines, which have a surface displacement of 2,800 tonnes – have already completed service-life extension work to date. The seven boats have received extensive refits during their second and third maintenance cycles, which have been planned to bring the vessels to “almost the same level of that of the latest model Sōryū-class submarine, while extending their service lives.[1]