The Nosaka Scandal

In my article "The forgotten story of Japanese communists in the Soviet Union", published on 21 March 2025, I discussed how Japanese communists residing in the Soviet Union were impacted by Stalin’s Great Terror (1936–38), drawing on the work of Japanese historian Tetsuro Kato. In this piece, once again informed by Kato’s research and other sources, I shall briefly recount how Sanzo Nosaka, one of the principal figures of the Japanese Communist Party (JKP), drove fellow party leader Kenzo Yamamoto and his wife to their deaths in the immediate aftermath of that grim period. This dramatic tale of betrayal, known as the Nosaka Scandal, remained concealed in the dark recesses of history for 53 years. It was only towards the close of the 20th century, in 1992—when Nosaka was still alive—that the truth resurfaced.

Sanzo Nosaka (1949)

Before delving into this tale of betrayal, let us briefly examine the life of Sanzo Nosaka (1892–1993), whose lifespan exceeded a century. Nosaka was a prominent figure in the Japanese communist movement. He played an active role in founding the JKP in 1922 and served as its leader for many years. Confronted with political repression in Japan, he sought refuge in the Soviet Union in late 1931. There, he worked on behalf of the Comintern (Communist International), acting not only as the JKP representative in Moscow but also as a member of the Executive Committee of the Comintern (ECCI). He was instrumental in drafting the ‘1932 Thesis’, which underpinned the ideological foundation of the JKP until 1946. Moreover, at the behest of the Comintern, he undertook intelligence operations in the United States.

In 1946, Nosaka returned to Japan, where he was elected to the Central Committee of the reconstituted JKP as well as to the lower house of the Diet (parliament). When the US occupation authorities expelled communists from Japanese politics during the Cold War, Nosaka went into hiding to evade arrest. In 1955, he resurfaced as the first secretary and leading figure of the JKP, calling for unity among communists.

Nosaka was subsequently elected to the House of Representatives in 1956, a position he held until 1977. In 1958, he was chosen as Chairman of the party's Central Committee. He retired from active politics in 1982 at the age of 90.

Kenzo Yamamoto (1892–1939), a contemporary of Nosaka, was also a significant figure in the Japanese communist movement. He had journeyed to the Soviet Union even before Nosaka, arriving in 1928, and served as the Japanese representative to the Red Trade Union International (Profintern). Following the death of Sen Katayama in 1933, he emerged as one of the foremost leaders of the Japanese communist group in the Soviet Union. He shared not only a political alliance with Nosaka but also a close personal friendship.

Kenzo Yamamoto

In 1992, Japanese journalists Akira Kato and Shunichi Kobayashi uncovered a letter written by Sanzo Nosaka, dated 22 February 1939, in archives that had been partially opened following the collapse of the Soviet Union. In this letter to the Comintern's Secretary General, Georgi Dimitrov, Nosaka detailed various suspicions regarding Kenzo Yamamoto, including that he was "an agent of Japanese imperialism". This denunciatory letter proved to be the final nail in the coffin for Yamamoto, who had been imprisoned since November 1937.

Yamamoto was executed by firing squad on 19 March 1939, shortly after Dimitrov received the denunciation letter. His wife, Matsu, was arrested and sent to a Gulag camp, where she ultimately perished. In 1963, Yamamoto and his wife were exonerated and their political reputations restored.

The discovery of Nosaka's denunciation letter in 1992 caused a great shock within the JKP. At the time, Nosaka was 100 years old and held the title of honorary chairman of the party, but he was swiftly expelled. Once revered as “the glorious face of party history,” he was now branded a “traitor and enemy of the party.” A year after his expulsion, in 1993, at the age of 101, he died in solitude and likely in disgrace.

We cannot say for certain why Nosaka penned this denunciation letter, as he never provided any explanation during his lifetime. It is possible that factors such as political jealousy, the relentless and even menacing pressures exerted by the NKVD, a desire to safeguard himself by delivering a decisive blow to a fallen comrade expected to be executed, or rumours of an affair between Yamamoto and Nosaka’s wife played a part. Whatever Nosaka's personal motivations may have been, it is clear that the noxious political and social climate engendered by Stalinist terror lay at the heart of these events.

On 6 March 1953, members of the JKP observe a minute's silence for Stalin at the party headquarters in Tokyo