Traditionally, welfare state research has claimed that leftists and their capacity to mobilize power resources are crucial factors in welfare state building. However, this chapter points out that such an approach may rest on the West-biased assumption that they are socio-economic reformists. Within the context of the Cold War, mainstream leftists in Japan and South Korea tended to place more of a priority on pacifism and nationalistic issues such as reunification than socio-economic issues. Furthermore, they adhered to radical ideologies such as Marxism–Leninism and Juche, making them hesitant to work towards the construction of a welfare state. Accordingly, the power resources of leftist groups in Japan and Korea have not been used for welfare state building.