It split off after its executive committee members had been expelled from Doro because of their support for Sanrizuka-Shibayama Union to Oppose the Airport.

[4] As of 1985, the union had 1,100 members,[5] and on November 28, 1985, it staged a strike to protest against the plans of the Prime Minister Yasuhiro Nakasone's government to privatize JNR and lay off workers.

The 24-hour strike caused 135 trains between Tokyo and Chiba prefecture to be cancelled, and JNR's management decided to fire more than 100 workers for staging the illegal walkout.

[7] Communications lines were cut, fires were set at 27 locations in seven prefectures, and heavy damage was done to Asakusabashi Station in Tokyo around 7 a.m. by masked figures wearing helmets and throwing firebombs.

Police raided offices of the Middle Core Faction and Doro-Chiba, and damage to bullet trail lines near Hiroshima that delayed trains between Tokyo and Kyushu appeared to have been caused by a time bomb[8] and by noon 48 people were arrested, including leaders of the Middle Core Faction.