In the pre-war period, the Tokyo Metropolitan Police Department established the Tokubetsu-keibi-tai. During the war, as air raids on Japan intensified and civilian casualties increased, TMPD Emergency Service Unit was enhanced for relief mission and renamed as Security Unit, and at the same time, it was decided to set up similar units in other prefectures with major cities. But all these units were disbanded in 1946 as the occupation progressed. On the same day, the Guard Section was created for the same role in the TMPD. In 1948, this unit was reinforced to the Police Reserve Units. In addition, similar but smaller-scale riot squads were created in several other prefectures to deal with post-war turmoil. In 1952, under the direction of the National Rural Police Headquarters, the Riot Police Units were created with 20 prefectures with large cities. In 1957, the TMPD Reserve Units were also renamed the Riot Police Unit. Until 1962, all PPHs had the same kind of units.
Organization
Riot police units comprise the main strength of the Security Departments of each Prefectural police headquarters. Most PPHs have only one unit, but some urban PPHs have multiple units. For example, there are ten units in the TMPD. Each units consist of a headquarters and some companies. The public relations divisions, known as "DJ cops", are placed in each unit headquarters. They rely on eloquent and humorous speaking to prevent crowd disasters.
Specialist squads
The equipment of the anti-riot officers is largely the same as that of regular police officers. However, equipment used in riot control operations, such as protective gear, may differ. And within the Riot Police Units, there are certain squads with specific equipment and training.
;Rescue squads ;Ranger Courses ;Water rescue squads Also, as non-permanent units prepared for large scale disasters, the Interprefectural emergency rescue units have been established based on the lesson of the Great Hanshin earthquake. Members of these units work mainly in Riot Police Units or Regional Riot Police Units during peacetime, but they regularly gather and train in preparation for disasters.
Reserves
Full-time riot police units can also be augmented by auxiliary riot police units with regular police officers trained in riot duties. There are two types of auxiliary riot police units: ;Secondary Riot Police Units ;Regional Riot Police Units
