 Destroyers of the JMSDF had been divided into two series, anti-aircraft gun fire oriented destroyers (DDA) and ASW-oriented destroyers (DDK).However, in the 1970s, a drastic review of the fleet became necessary due to the enhancement of the Soviet submarine fleet and the reinforcement of the anti-ship missiles.After consideration by Operations research, eight ships / eight helicopters concept was adopted as a new fleet organization.