Hibiya Incendiary Incident (日比谷焼討事件 Hibiya Yakiuchi Jiken ) was a major city-wide riot which erupted in Tokyo on 5 September 1905 in protest of the terms of the Treaty of Portsmouth, which ended the Russo-Japanese War of 1904-1905.
Although the Imperial Japanese Navy had decisively defeated the Imperial Russian Navy at the Battle of Tsushima, and the Imperial Japanese Army had taken Port Arthur and had won a major victory over the Imperial Russian Army at the Battle of Mukden, Japanese forces were overextended in Manchuria, and the Japanese economy could no longer sustain a prolonged war effort. Ignorant of the actual war situation, a diverse assortment of activist groups called for a rally at Hibiya Park in central Tokyo to protest what they saw as the humiliating terms of the Treaty of Portsmouth, announced earlier that day. The protesters were especially incensed that Japanese territorial gains in the Liaodong Peninsula and the northern half of Sakhalin were to be returned to Russia, and that the Russian government would not pay any war reparations to Japan.
A crowd began to gather at Hibiya Park early in the evening of 5 September 1905 only to find that the police had banned the rally and barricaded the park gates. The crowd swelled to about 30,000 people, but the police still refused to open the gates. The crowd then turned riotous, marched towards the Imperial Palace grounds, and rampaged across the city for the next two days.
Before order was finally restored, angry mobs had destroyed or damaged more than 350 buildings, including the residence of the Home Minister and 70 percent of the police boxes in the city. Casualties included 17 people killed, over 450 policemen, 48 firemen and civilians injured, and hundreds arrested. News of the Tokyo violence touched off similar disturbances in Kobe and Yokohama and further stimulated hundreds of nonviolent rallies, speeches, and meetings throughout Japan for the next several months. This unrest directly contributed to the collapse of Prime Minister Katsura Taro's cabinet on 7 January 1906.
The Hibiya Incendiary Incident marks the beginning of a period in Japanese history that historians call the Era of Popular Violence (民衆騒擾期 minshū sōjō ki ). Over the next 13 years Japan would be rocked by a series of violent protests (nine different riots in Tokyo alone), culminating in the Rice Riots of 1918.