The Communist Party of Great Britain (CPGB) was founded in 1920 and dissolved in 1991. It was founded at the behest of V.I. Lenin and was formed by the merger of the British Socialist Party, the Socialist Labour Party (based on 'Red Clydeside') and the Workers' Socialist Federation, run by Sylvia Pankhurst. From the start it received support and orders from the Soviet Union, directed through the Moscow-based standing organisation of the Third Communist International, better known as Comintern.
In the years between its foundation and the outbreak of the Second World War the CPGB was successful in building up membership and support. It was able to benefit from the seeming inability of more mainstream parties to successfully act against rising unemployment and economic crisis, and against the rise of Fascism. It alternated between policies (decided in Moscow and applied worldwide, even if contradicting local political circumstances) of sectarian opposition to other left-of-centre parties, and attempts to build up a 'popular front' with socialists and social democrats. It also attracted the support of many intellectuals and was able to pose as a revolutionary artistic vanguard. Communists contributed much of the manpower (and most of the political control) to the Clement Attlee Brigade of British volunteers in the International Brigades during the Spanish Civil War.
The CPGB and the Second World War
The Ribbentrop-Molotov Pact of 1939 led Comintern to instruct the CPGB to oppose the war (which it had been supporting as an anti-Fascist war). This caused much internal dissent and defection, as well as the dropping of its long-time General Secretary, Harry Pollitt (1890-1960). The CPGB newspaper, the Morning Star, was for a time suppressed by the British Government. However, following the German invasion of the Soviet Union in June 1941 Pollitt was recalled, the party threw itself into the war effort, and Communist officials were active in attempts to prevent strikes.
The post-war years
The party emerged from the war at the peak of its popularity and prestige. Two Communist MPs were elected at the 1945 general election, and membership was at a peak. Comintern had been dissolved in 1943, and the party was theoretically free to decide its own policies. However, it remained ideologically linked to the Soviet Union, and over succeeding decades membership fell away as the nature of Soviet rule became increasingly apparent in the west and as the Cold War took hold of global foreign policy decisions. Major crisis points were the Soviet interventions in Hungary in 1956 (which saw a huge drop in membership) and that in Czechoslovakia in 1968.
By the later 1960s and 1970s the party, bereft of MPs and a popular voting base, decided to concentrate on exploiting its influence within the trades union movement. This was to be relatively successful - members and sympathisers held several senior positions in the movement - but was to backfire spectacularly as popular disquiet at what was perceived as excessive and irresponsible trade union power was a major factor in securing the election of a Conservative Party government under Margaret Thatcher in 1979.
Conservative trade union reforms demolished the CPGB industrial strategy; reformist government in the Soviet Union was to bring and end to the Cold War and to the eastern bloc monolith itself. However, neither of these factors was decisive in bringing about the demise of the CPGB. Instead, it tore itself apart in a series of feuds between hard-line 'tankies' and reformist 'Eurocommunists'; eventually, the disputes were as much about control of the party assets and the party newspaper (by now renamed the Morning Star) as they were about ideological differences.
End of the CPGB
In 1977 one hard-line faction left the party to become the New Communist Party, while in 1988 a major split occurred when a large number of 'tankies' left to form the Communist Party of Britain. The residual CPGB decided in 1991 to dissolve itself and reform itself as Democratic Left; this also dissolved in the late 1990s and was refounded as New Politics Network; in 2006 NPN started the process of merger with the British constitutional reform campaign group Charter 88 under the name Unlock Democracy
Francis Beckett, Enemy Within: The Rise and Fall of the British Communist Party (2nd ed Woodbridge, Suffolk, UK 1998)