This article uses the Scottish and Welsh Councils for Nuclear Disarmament as windows into the relationship between peace and nationalism in Scotland and Wales in the late 1950s and early 1960s. From one perspective, it challenges histories of peace movements in Britain, which have laboured under approaches and assumptions centred on London. From another, it demonstrates the role of movements for nuclear disarmament in the emergence of a ‘left of centre’ nationalism in Scotland and Wales. Although these movements were constituents of the British Campaign for Nuclear Disarmament, their nationalism evolved as the threat from nuclear weapons to Scotland and Wales came to be seen as distinctive and was interpreted through lenses of local culture and tradition. The movements contributed to ‘the making of national identity’ by providing a channel through which activists could ‘nationalize’ and galvanize Scottish and Welsh Christianity, folk and socialism in particular. It was through the movements that activists articulated and promoted Scotland and Wales as sovereign nations of peace, with an international outlook separate from that of Britain.