The Leftist Socialist Party of Japan was a Japanese

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

 political party that existed between 1948 and 1955. It was a radical socialist political party, which adopted Marxism-Leninism

Marxism-Leninism

Marxism–Leninism is a communist ideology, officially based upon the theories of Marxism and Vladimir Lenin, that promotes the development and creation of a international communist society through the leadership of a vanguard party over a revolutionary socialist state that represents a dictatorship...

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History

Following the defeat of the Japan Socialist Party (JSP) in 1948 at the hands of Japan's two main conservative

Conservatism

Conservatism is a political and social philosophy that promotes the maintenance of traditional institutions and supports, at the most, minimal and gradual change in society. Some conservatives seek to preserve things as they are, emphasizing stability and continuity, while others oppose modernism...

 parties, the Liberal Party

Liberal Party (1945)

was a right-wing party in Japan, founded on November 9, 1945, mainly by former members of Seiyukai Party. Its first leader was Ichirō Hatoyama. In 1946-1947 and 1948-1954, the next party leader Shigeru Yoshida was the Prime Minister....

 and the Democrat Party

Democratic Party (1947)

Democratic Party was a right-wing political party in Japan. It was founded in spring 1947 by merging the Progressive Party of Inukai Takeru with a faction of Liberal Party led by Hitoshi Ashida and obtained 124 seats in 1947 elections. The party had held seven seats in Tetsu Katayama's government...

, the Japan Socialist Party dissolved into chaos and internal bickering between moderates and Marxist-Leninists. As a result the JSP split: some of its members formed a moderate

Moderate

In politics and religion, a moderate is an individual who is not extreme, partisan or radical. In recent years, political moderates has gained traction as a buzzword....

 and almost centrist social-democratic party, while others formed a more radical, socialist, and Marxist-Leninist party. Both groups claimed the name "Japan Socialist Party" and are known as the Rightist Socialist Party of Japan

Rightist Socialist Party of Japan

The Rightist Socialist Party of Japan was a Japanese political party that existed between 1948 and 1955. It was a center-left political party, which adopted a policy of moderate social-democracy.- History :...

 and Leftist Socialist Party of Japan, respectively.

The left-wing was in chaos between 1948 and 1955, and in early 1955 the Rightist Socialists and the Leftist Socialists reconciled and merged to reform the JSP, months before the Liberal Democrat Party

Liberal Democratic Party (Japan)

The , frequently abbreviated to LDP or , is a centre-right political party in Japan. It is one of the most consistently successful political parties in the democratic world. The LDP ruled almost continuously for nearly 54 years from its founding in 1955 until its defeat in the 2009 election...

 was created through a merger of the Liberal and Democrat Parties. The Leftist Socialists generally had the upper hand in the reunified JSP, causing a few rightists to leave the Party in 1960 to create the Democratic Socialist Party

Democratic Socialist Party (Japan)

The was a social democratic party in Japan.- History :The Democratic Socialist Party was established in 1960 by a breakaway group of the Japan Socialist Party. It was made up of many members of the former Rightist Socialist Party of Japan, a moderate social-democratic faction that existed...

.

On domestic policy, the party was radical socialist, Marxist-Leninist and left-wing. It is now defunct.