In the immediate aftermath of the earthquake, law and order broke down in many parts of the affected region. This period was characterized by the spread of rumors, the formation of vigilante groups (), and the
massacre of ethnic Koreans and other mistaken for them, as well as the murder of political activists by the authorities.
Rumors and misinformation Widespread destruction of communication infrastructure contributed to an atmosphere of uncertainty and fear. Rumors spread rapidly, often relayed by refugees fleeing the disaster zone. Some stories suggested that
Mount Fuji had erupted or that a large tsunami had washed away Yokohama. The most damaging rumors, however, concerned alleged activities by Koreans. Originating from looting by Japanese in Yokohama that was misattributed to Koreans, false reports circulated that Koreans were poisoning wells, committing arson, looting, and organizing attacks on Japanese. These rumors were given a degree of legitimacy when some government officials, including
Gotō Fumio of the
Home Ministry, broadcast messages warning of "organized groups of Korean extremists" attempting to "commit acts of
sedition". On 2 September, the police headquarters, lacking manpower to confirm eyewitness reports, passed them on as factual and issued a statement that "unscrupulous Koreans are committing acts of arson and other forms of violence".
Massacre of Koreans and others Fueled by these rumors and a climate of fear and
xenophobia, Japanese vigilante groups, known as , formed across the Kantō region. By mid-September, an estimated 3,689 such groups were operating, ostensibly to prevent fires, stop looting, and maintain order. However, many of these groups, often armed with makeshift weapons like clubs, swords, and bamboo spears, targeted Koreans and, in some cases, Chinese,
Okinawans, and Japanese from certain regions who were mistaken for Koreans due to their accents. Estimates of the death toll in what became known as the
Kantō Massacre vary significantly. Police confirmed the deaths of 248 Koreans, while an investigation by the Governor-General of Korea determined 832 had been killed or were missing. A separate investigation by Korean students concluded that 2,613 Koreans had been killed; some modern estimates reach as high as 6,000. Victims were often subjected to brutal violence, including beatings, stabbings, and
lynchings, sometimes after being "tested" for their Korean identity (e.g., by being asked to pronounce Japanese
words that were difficult for Koreans). While some police and military personnel attempted to protect Koreans, others were complicit in the violence or turned a blind eye. Although police made belated corrections to the rumors on 3 and 4 September, few perpetrators were prosecuted; of 125 vigilante group members tried, only 32 received formal sentences, and 91 received suspended sentences. Contemporary commentators like Hoashi Ri'ichirō and Oku Hidesaburō condemned the massacres as "extremely disgusting and internationally shameful" and a "disgraceful act that exposed a moral flaw". The chaos also provided a cover for the murder of political dissidents. The most prominent case was the
Amakasu Incident, in which the anarchist
Sakae Ōsugi, his partner
Noe Itō, and his six-year-old nephew were arrested and then brutally killed by a squad of military police led by Lieutenant
Masahiko Amakasu.
Cabinet response and martial law The earthquake struck at a time of political uncertainty in Japan. Prime Minister
Katō Tomosaburō had died on 24 August, and Admiral
Yamamoto Gonnohyōe, selected to form a new cabinet, had not yet succeeded when the disaster occurred. The disaster also forced the postponement of Crown Prince
Hirohito's marriage and accession ceremonies. This elite-level political vacuum contributed to confusion over who had the authority to deploy police and military personnel. General Ishimitsu Maomi, deputy commander of the Imperial Guard Forces, acted first, deploying troops to protect imperial locations. Akaike Atsushi, inspector general of the
Tokyo Metropolitan Police, faced an overwhelming task with outnumbered and unprepared forces. The new cabinet was formally appointed on the afternoon of 2 September, sworn in on the lawn of the
Akasaka Detached Palace amid falling ash, as other ministerial buildings were deemed unsafe. (left) holding a cabinet meeting outdoors for fear of further building collapses amid aftershocks One of the first decisions of the new cabinet was to declare
martial law over what remained of the capital on 2 September. This ushered in the largest peacetime domestic mobilization and deployment of the army in Japan's pre–
World War II history, with eventually over 52,000 troops deployed to Tokyo and Yokohama. The martial law headquarters was granted extensive powers, including administering relief and public safety, prosecuting lawbreakers, prohibiting public gatherings, censoring information, stopping and searching individuals, and entering private homes. Martial law remained in effect until 15 November. Initial military deployment was fraught with difficulties. Commanders arriving in Tokyo found a near total absence of reliable information and lines of communication were non-existent. The military had to rely on
aerial reconnaissance and around 2,000 army-trained
carrier pigeons for communication. The zone of martial law was progressively expanded to cover all of Tokyo and Kanagawa Prefectures by 3 September, and Chiba and Saitama Prefectures by 4 September. To counter rumors and vigilante violence, particularly against Koreans, military authorities were empowered to arrest individuals, disband suspicious groups, and confiscate weapons. From 4 September, military and police began to collect and transport Koreans to government-run detention centers for "protective custody"; by the end of September, 23,715 Koreans had been taken into these centers. == Relief efforts ==