Overview In the 1960s,
leftist student movements pervaded Japan's universities, as similar movements did in the West. By the latter half of the decade, these movements had become very factionalized, competitive, and violent. After a series of incidents in which leftist student groups injured or killed law enforcement officials and civilians, the
National Police Agency cracked down on these groups, raiding their hideouts and arresting dozens in 1971 and 1972. Attempting to conceal themselves from the police, a core group of radicals from the
United Red Army (URA) retreated to a compound in
Gunma Prefecture during the winter of 1972.
Obtaining guns and cash The two groups that later merged into the
United Red Army independently carried out violent acts in early 1971. The
Keihin Anti-Security Treaty Joint Struggle Group, led by
Hiroko Nagata and Hiroshi Sakaguchi, raided a gun shop in
Mooka (
Tochigi Prefecture) on February 17, acquiring 9 shotguns, 1 rifle, 1 airgun, and 2300 rounds of ammunition. Panicked by the prompt response of the police, most raiders escaped by car but two were left behind; once arrested, they identified the culprits, resulting in Nagata, Sakaguchi, and the others being placed on the wanted list. Separately, the
Red Army Faction led by
Tsuneo Mori, and including Kunio Bandō (who is still at large), carried out a series of robberies—4 banks, 3 post offices, and an elementary school—over the period February 22 to July 23, 1971 (referred to by police as "Operation M", for "money"). At the time, leftist student demonstrations were losing momentum, but other than a few journalists and security specialists, no one had heard of these groups before.
Mountain hide-outs The police launched a nationwide manhunt, making it impossible for perpetrators to hide, even in distant cities such as
Sapporo and
Kyoto; both groups decided to converge in the mountainous area of NW
Gunma Prefecture. The Keihin Group went to the mountainous area of
Gunma Prefecture and set up
agitpunkt (agitation points; an aggressive name for a hide-out), collectively the "mountain base" (separate bases on the slopes of
Mount Haruna, Mount Kasho, and
Mount Myōgi). Separately, the Red Army Faction left the cities and set up an
agitpunkt in
Yamanashi Prefecture (the Niikura Base). Using funds from the robberies, the URA purchased weapons from the Keihin Group, and in early December 1971 the first joint military exercises were held between the two groups (29 members total). However, a faction emerged within the Keihin Group that resisted integration. On 18 December, radio news announced that , a member of the Keihin group still in the Tokyo area, had been shot to death during an assault on a police station in
Itabashi. On 20 December, the first leadership conference of the combined groups was held at the Haruna base of the Keihin Group. The leaders knew that the police were aware of their general location, and it would be difficult to leave the mountains. Without hope of outside help or escape, in late 1971, the leaders of the two factions, Mori and Nagata, planned a which required an ideological review process of criticism and
self-criticism of all members.
Internal purge It was at the Gunma compound, on the second week of February 1972, that URA chairman
Tsuneo Mori and vice-chairman
Hiroko Nagata initiated a violent
purge of the group. Nagata and Mori directed the deaths by beating of eight URA members, as well as one non-member who happened to be present. Six other members were tied to trees outside, where they froze to death in the frigid weather. On February 16, police arrested Mori, Nagata, and six other URA members at either the compound or at a nearby village. Five others, armed with rifles and shotguns, managed to escape, fleeing on foot through the mountains towards the community of
Karuizawa in nearby
Nagano Prefecture. These five fugitives were Kunio Bandō (25), a graduate of
Kyoto University; Masakuni Yoshino (23), a senior at
Yokohama National University; Hiroshi Sakaguchi (25) a dropout of
Tokyo Suisan University; Jirō Katō (19), and his brother Saburō Katō (16). == Incident ==