US-Japan Foreign and Defense Talks ‘Extended Nuclear Deterrence’, ROK-US Defense ‘US Nuclear NCG Limited’ In the US-Japan system, the establishment of the Joint Joint Operations Command (JJOC) of the Self-Defense Forces was agreed upon for ‘extended nuclear deterrence’, while the ROK-US system was limited to the ‘ROK-US Nuclear Consultative Group (NCG)’ excluded from the ‘nuclear umbrella’, conf..