In the Spanish Civil War, the CPGB worked with the USSR to create the British Battalion of the International Brigades,[11] which party activist Bill Alexander commanded.

Many key CPGB members served as leaders of Britain's trade union movement, including most notably Jessie Eden, David Ivon Jones, Abraham Lazarus, Ken Gill, Clem Beckett, GCT Giles, Mike Hicks, and Thora Silverthorne.

The CPGB's position on racial equality and anti-colonialism attracted many black activists to the party, including Trevor Carter, Charlie Hutchison, Dorothy Kuya, Billy Strachan, Peter Blackman, George Powe, Henry Gunter, Len Johnson, and Claudia Jones, who founded London's Notting Hill Carnival.

A few days after the founding conference the new party published the first issue of its weekly newspaper, which was called the Communist and edited by Raymond Postgate.

Lenin argued that if such organisations gained power, they would demonstrate that they were not really on the side of the working class, thus workers would become disillusioned and come over to supporting the Communist Party.

Initially, therefore, the CPGB attempted to work within the Labour Party, which at this time operated mainly as a federation of left-wing bodies, only having allowed individual membership since 1918.

[20] In the aftermath of the Campbell Case and the Zinoviev letter, Labour expelled Communist Party members and banned them from running as its parliamentary candidates in the future.

[23] Some of the key activists charged with this task, Philip Spratt and Ben Bradley, were later arrested and convicted as a part of the Meerut Conspiracy Case.

At the same time, Asian and African delegates to the Comintern such as Ho Chi Minh, M. N. Roy, and Sen Katayama criticized the GBCP for neglecting colonial issues in India and Ireland.

This cadre of which Hannington and Harry MacShane in Scotland were emblematic, found a purpose in building the NUWM which resulted in a number of marches on the unemployment issue during the 1930s.

This policy argued that as fascism was the main danger to the workers' movement, it needed to ally itself with all anti-fascist forces including right-wing democratic parties.

With the beginning of the Second World War in 1939, the CPGB initially continued to support the struggle on two fronts (against Chamberlain at home and Nazi fascism abroad).

Trade unionists in the party in 1968 included John Tocher, George Wake, Dick Etheridge and Cyril Morton (AEU); Mick McGahey, Arthur True and Sammy Moore (NUM); Lou Lewis (UCATT) and Max Morris (NUT).

The Broad Left went on to help elect Ray Buckton (ASLEF), Ken Cameron (FBU), Alan Sapper (ACTT) and Jack Jones (TGWU) in 1969.

Perhaps the best known of the tiny minority of CPGB members who opposed the Moscow line was Michael McCreery, who formed the Committee to Defeat Revisionism, for Communist Unity.

Later a more significant group formed around Reg Birch, an engineering union official, established the Communist Party of Britain (Marxist-Leninist).

[citation needed] Divisions in the CPGB concerning the autonomy of the party from Moscow reached a crisis in 1968 when Warsaw Pact forces invaded Czechoslovakia.

From this time onwards, the most traditionally-minded elements in the CPGB were referred to as 'Tankies' by their internal opponents, due to their support of the Warsaw Pact forces.

[41] The last strong electoral performance of the CPGB was in the February 1974 General Election in Dunbartonshire Central, where candidate Jimmy Reid won almost 6,000 votes.

Nationally the party's vote continued its decline: according to a contemporary joke, the CPGB at this time pursued the British Road to Lost Deposits.

[42] Dave Cook became National Organiser in 1975 and Sue Slipman was appointed to the executive committee and to the Marxism Today editorial board.

[43] Beatrix Campbell (a contributor, with Slipman, to Red Rag) and Judith Hunt became active in the National Women's Advisory Committee.

Its turn to Eurocommunism was prefigured by what Andrews describes as Sarah Benton's "radical and heretical" stint as editor of the fortnightly review Comment.

At the 1975 Congress, economist Dave Purdy proposed that "the labour movement should declare its willingness to accept voluntary pay restraint as a contribution to the success of the programme and a way of easing the transition to a socialist economy"[45] – a challenge to the Industrial Department's policy of "free collective bargaining".

Jimmy Reid, Cyril Morton and John Tocher had all been members of the Political Committee, playing a crucial role in determining the direction of the party.

The New Communist Party of Britain was formed under the leadership of Sid French, who was the secretary of the important Surrey District CP, which had a strong base in engineering.

"[47] In 1984, a long-simmering dispute between the majority of the leadership and an anti-Eurocommunist faction (associated with party industrial and trade union activists) flared up when the London District Congress was closed down for insisting on giving full rights to comrades who had been suspended by the executive committee.

After the General Secretary closed the Congress a number of members remained in the room (in County Hall in South London) and held what was, in effect, the founding meeting of a breakaway party, although the formal split did not come until four years later.

[55] "Tankie" is a pejorative term referring to those members of the Communist Party of Great Britain who followed the Kremlin line, agreeing with the crushing of the revolution in Hungary and later the Prague Spring by Soviet tanks; or more broadly, those who followed a traditional pro-Soviet position.

[citation needed] The term is currently used in a somewhat broader sense in Internet slang to refer to any practitioner of far-left politics, especially Marxism–Leninism or Maoism, and particularly those who refute the accusations of authoritarianism and human rights abuses of certain Marxist states, such as the former Soviet Union, China, Cuba and Vietnam.