Japan Socialist Party in the context of "Democratic Party of Japan"

The 1955 system (Japanese: 55年体制, Hepburn: 55-nen Taisei), also known as the one-and-a-half party system, is a term used by scholars to describe the dominant-party system that has existed in Japan since 1955, in which the Liberal Democratic Party (LDP) has held by itself or in coalition with Komeito (from 1999 to 2025) a government nearly uninterrupted, with opposition parties largely incapable of forming significant or long lasting alternatives, other than for brief stints in 1993–1994 and 2009–2012. The terms 1955 system and the one-and-a-half party system are credited to Junnosuke Masumi [ja], who described the 1955 system as "a grand political dam into which the history of Japanese politics surge".

The years of Japan under the 1955 regime witnessed high economic growth, leading to the dominance of the ruling party in the Diet, with an undergirded tight connection between the bureaucracy and the business sector. Due to a series of LDP scandals and the 1992 burst of the Japanese asset price bubble, the LDP lost its majority in the House of Representatives in the 1993 general election, which initially signalled the end of the 1955 system. However, the left-wing Japan Socialist Party, the long-time opposition which finally gained a majority, would soon lose much of its support after it decided to form a coalition government with the arch-rival LDP just a year later, leading to the JSP being refounded as the SDP in 1996, and its coalition partner regaining power. The LDP briefly lost power again in 2009 to the now defunct Democratic Party of Japan before regaining it in 2012, retaining power up to the present day. Nevertheless, it lost its majority in the House of Representatives in the 2024 general election, and its majority in the House of Councillors in the 2025 election, forcing it to run a minority government for the first time.

35°45′55″N 140°23′08″E / 35.76528°N 140.38556°E / 35.76528; 140.38556The Sanrizuka Struggle (三里塚闘争, Sanrizuka tōsō) is a series of civil conflicts and riots involving the Japanese government and the agricultural community of Sanrizuka, comprising organised opposition by farmers, local residents, and leftist groups to the construction of Narita International Airport (then New Tokyo International Airport). The struggle stemmed from the government's decision to construct the airport in Sanrizuka without the involvement or consent of most area residents.

The struggle was led by the Sanrizuka-Shibayama United Opposition League against Construction of the Narita Airport (ja:三里塚芝山連合空港反対同盟, Sanrizuka-Shibayama Rengo Kūkō Hantai Dōmei), which locals formed under the leadership of opposition parties the Communist Party and Socialist Party. The struggle resulted in significant delays in the opening of the airport, as well as deaths on both sides.

Nobusuke Kishi (岸 信介, Kishi Nobusuke; 13 November 1896 – 7 August 1987) was a Japanese bureaucrat and politician who served as prime minister of Japan from 1957 to 1960. He is remembered for his exploitative economic management of the Japanese puppet state of Manchukuo in China in the 1930s, imprisonment as a suspected war criminal following World War II, and provocation of the massive Anpo protests as prime minister, retrospectively receiving the nickname "Monster of the Shōwa era" (昭和の妖怪; Shōwa no yōkai). Kishi was the founder of the Satō–Kishi–Abe dynasty in Japanese politics, with his younger brother Eisaku Satō and his grandson Shinzo Abe both later serving as prime ministers of Japan.

Born in Yamaguchi Prefecture, Kishi graduated from Tokyo Imperial University in 1920. He rose through the ranks at the Ministry of Commerce and Industry, and during the 1930s led the industrial development of Manchukuo, where he exploited Chinese slave labor. Kishi served in the wartime cabinet of Hideki Tōjō as minister of commerce and industry from 1941 to 1943 and vice minister of munitions from 1943 to 1944. At the end of the war in 1945, Kishi was imprisoned as a suspected Class A war criminal, but U.S. occupation authorities did not charge, try, or convict him, and released him in 1948 during the Reverse Course. At the end of the occupation in 1952, Kishi was de-purged, enabling his election to the National Diet in 1953. With overt and covert U.S. support, he consolidated Japanese conservatives against perceived threats from the Japan Socialist Party, and in 1955 was instrumental in forming the Liberal Democratic Party (LDP). Kishi was thus key in establishing the "1955 System" under which the LDP remains Japan's dominant party.

General elections were held in Japan on 6 July 1986 to elect the 512 members of the House of Representatives, alongside elections for the House of Councillors. The result was a landslide victory for the ruling Liberal Democratic Party (LDP), which gained 50 seats and an outright majority in the House. The LDP's 300 seats remains its joint-best general election result.

Most opposition parties lost seat, the exceptions being the Japanese Communist Party (which remained at 26 seats) and the Socialist Democratic Federation, which gained one seat. The biggest losses were experienced by the Japan Socialist Party, which lost 27 seats. The Democratic Socialist Party saw a 12-seat loss, while Kōmeitō saw a loss of three seats and the New Liberal Club, which had been in coalition with the LDP, lost two seats.

Zenkō Suzuki (鈴木 善幸, Suzuki Zenkō; 11 January 1911 – 19 July 2004) was a Japanese politician who served as prime minister of Japan from 1980 to 1982.

Born in Iwate Prefecture, Suzuki graduated from the Tokyo University of Fisheries in 1935 and was elected to the Diet in 1947 as a member of the Japan Socialist Party, then shifted rightward and joined the Liberal Democratic Party. He briefly served as posts and telecommunications minister and cabinet secretary under Hayato Ikeda, as health and welfare minister under Eisaku Satō, and as agriculture, forests, and fisheries minister under Takeo Fukuda. After the sudden death of prime minister Masayoshi Ōhira in 1980, Suzuki assumed leadership of his faction, and he succeeded him as LDP president and prime minister until 1982.

Tsutomu Hata (羽田 孜, Hata Tsutomu; 24 August 1935 – 28 August 2017) was a Japanese politician who briefly served as prime minister of Japan in 1994.

Born in Tokyo, Hata graduated from Seijo University and was first elected to the National Diet in 1969. He rose to become a key member of the Liberal Democratic Party's Tanaka/Takeshita faction, and served as agriculture, forests, and fisheries minister in the 1980s and finance minister from 1991 to 1992. After Keizō Obuchi took over the faction, Hata formed the Japan Renewal Party in 1993, which joined in the anti-LDP coalition which formed Morihiro Hosokawa's government. Hata served as foreign minister, then replaced Hosokawa as prime minister when he resigned. However, the Japan Socialist Party soon left the coalition, causing it to collapse. Hata lost leadership of his party when it merged with the New Frontier Party, then formed his own Sun Party, which in turn merged with the Good Governance Party then Democratic Party in 1998. Hata became secretary-general of the party, and remained one of its senior advisors until his death.