The Asama-Sansō incident was a hostage crisis and police siege at a mountain lodge near Karuizawa in Nagano Prefecture, Japan, which lasted from February 19 to February 28, 1972. The police rescue operation on the final day of the standoff was the first marathon live television broadcast in Japan, lasting 10 hours and 40 minutes.

Riot Police Unit are the rapid reaction forces of Japanese prefectural police. These units are not only riot police, but a type of emergency service unit to maintain public order against large civil disorder, disaster response, or other emergency situations as the key units of Japanese law enforcement for crisis management. They are operated by prefectural police headquarters (PPH) under the supervision of the Security Bureau of the National Police Agency.