In early 1946, the newly legalized Japan Communist Party sought to establish a rival labor movement to the more conservative Sōdōmei federation.
In these early phases, the American Occupation authorities even encouraged the formation of Sanbetsu, believing it to be a necessary counterweight to Sōdōmei, which they viewed as having been too compliant with the militarist Japanese government's demands in the prewar period.
[3] However, in the late 1940s, with advent of the global Cold War, Occupation authorities began to view the activities of the militant Sanbetsu-affiliated labor unions with increasing alarm.
With the open encouragement of Occupation authorities, more conservative elements within the Sanbetsu-affiliated labor unions began to form “democracy cells” (mindō).
[5] Amidst the collapse of Sanbetsu during the Red Purge of 1950, these mindō rose to the fore and merged with some elements of Sōdōmei to form the new Sōhyō labor federation, with Kokurō as a leading member.
There was a government pledge that no one would be "Thrown out onto the street",[11] so unhired workers were classified as "needing to be employed" and were transferred to the JNR Settlement Corporation, where they could be assigned for up to three years.
23 years after the original privatization, on June 28, 2010, the Supreme Court settled the dispute between the workers and the Japan Railway Construction, Transport and Technology Agency, the successor body to the JNR Settlement Corporation.