|Second Japanese Civil War|
| Council of National Salvation (1918–1919)|| Empire of Japan
|Commanders and leaders|
| Nagayama Yoshida|
| Fushimi Sadanaru|
Japan's participation on World War I and Siberian Intervention brought the country into industrial booming. Exports quadrupled from 1913 to 1918. The massive capital influx into Japan and the subsequent industrial boom, however, led to rapid inflation. Japan succumbed into deep economic crisis and general dissatisfaction emerged among the populace against the country's expansionist policies. On July 1918, protests and disturbances against high prices of rice caused by this inflation erupted in villages and cities throughout Japan. This series of political disturbances then known as the Rice Riots of 1918.
By August 11, the riots had spread to the rest of the Kansai region; Osaka, Kobe, Kure and Hiroshima all experienced rioting, followed by Tokyo the next day. The largest cities in the industrial areas of Kansai and Kanto saw riots last up to a week, such as in Nagoya that lasted the longest at ten days. Beside the peasants and the urban population, the workers soon also involved on the disturbances by mounted strikes for better wages and working conditions.
On September 11, 1918, at the middle of country-wide crisis, Emperor Keishin suddenly died of influenza and it resulted to a disturbance among the country's elites since the Emperor not bore any son which created a vacuum on the throne succession. Prince Fushimi Sadanaru, from the Fushimi branch of the Imperial Family of Japan, was then appointed as sesshō-no-miya, the Prince Regent of the Empire of Japan. At the time of Emperor's death, the riots increased as many young soldiers deserted and switched their supports to the protestors.
The disturbances reached its climax on November 13, 1918. More than 5,200 demonstrators gathered in Hibiya Park, Tokyo, in protest against the government's economic policy and overspending on the military investiture. When the demonstrators marched from the park and approached toward the Imperial Palace, the Imperial Guards opened fire on the masses, killed 50 individuals and injured 327 others.
The revolutionary uprisings soon spread throughout Japan. At that time, there were many revolutionary groups in Japan, such as the radical nationalist Kenkokukai which based on Nagoya and left-leaning Proletarian Union under Katayama Sen. However, none of this groups that being well organized. The only nationalist group that very well organized, but yet supported the revolution was the Constitutional Nationalist Party under Inukai Tsuyoshi and Nagayama Yoshida.
On December 1, 1918, Inukai Tsuyoshi resigned as the party chairman and replaced by Nagayama Yoshida as the new chairman and Kita Ikki as the general secretary. Under Nagayama and Kita co-leadership, the party dropped its "Constitutional" name and now simply known as the "Nationalist Party". The Nationalist Party under Nagayama and Kita then formally declared its support to the revolution on December 3, 1918 and resigned all of its delegates from the Imperial Senate. Smaller revolutionary nationalist groups soon merged with the Nationalist Party. The Nationalists then moved its headquarters to Kyoto by December 21, 1918.
The National Congress of Japan that dominated by the Nationalists was convened in Kyoto on January 11, 1919 and adopted a motion that known as the Kyoto Declaration on January 14. The motion itself called for the formation of Council of National Salvation as the unified military command of the revolutionary forces and the immediate takeover of national government by the revolutionary movement. Nagayama was elected as its chairman. In response with the formation of Council of National Salvation, the Imperial Diet of Japan established the Supreme Military Command that headed by Prince Kan'in Kotohito to restore law and order in the country as well as to suppress the revolt.
The Provisional Revolutionary Government of Japan was established on January 24, 1919 with Inukai Tsuyoshi as its formal head. On February 16, 1919, co-incided with the date of traditional National Independence Day of Japan, the representatives from all provinces of Japan as well as from various political parties and interest groups was convened in a National Congress in the Kyoto City Hall and adopted the declaration of the establishment of the Republic of Japan.