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Paper short abstract

In the 1970s, Japan’s Democratic Socialist Party (DSP) accepted the Japan–U.S. Security Treaty. This shift was not simply a turn to realism or hawkishness, but reflected détente and broader changes in social democratic foreign policy, while the DSP retained its democratic socialist identity.

Paper long abstract

In postwar Japan, foreign policy was long structured by an ideological confrontation between conservative support for the Japan–U.S. alliance (Anpo) and leftist advocacy of unarmed neutrality. In the 1970s, however, this opposition underwent a significant transformation. While the Liberal Democratic Party maintained long-term rule and the Japan Socialist Party remained the principal opposition force, movements toward accepting the Japan–U.S. security framework emerged from other opposition parties. Most notably, this shift was embodied by the Democratic Socialist Party (DSP).

Conventional explanations for the DSP’s acceptance of Anpo emphasize its alleged turn toward political realism or increasing hawkishness. Although not entirely unfounded, such interpretations are overly simplistic. During this period, the DSP continued to affirm its ideological commitment to democratic socialism and actively strengthened ties with West European social democratic parties. Far from abandoning ideology, the party increasingly presented itself as a leading representative of democratic socialism in Japan and remained within the broader framework of the political left.

This paper argues that the DSP’s shift toward accepting Anpo in the 1970s should be understood in the context of global détente and changing priorities within social democratic foreign policy. Certainly, the end of the Vietnam War reduced fears that Japan would be drawn into U.S. military conflicts, while China and the Soviet Union’s acceptance of the Japan–U.S. security arrangement contributed to a more favorable domestic climate toward the alliance. Yet equally significant was the DSP’s growing emphasis on emerging global issues, particularly the North–South problem, to which the party devoted exceptional political energy.

In this respect, the DSP’s stance resembled that of West German Social Democrats under Willy Brandt, who reconciled social democracy with NATO while promoting international solidarity through initiatives such as the Brandt Commission on North–South issues. The DSP’s acceptance of Anpo thus reflected a broader trend within contemporary social democracy: prioritizing cooperation on global issues over asserting leftist distinctiveness in national security policy.