G.D.H. Cole was one of the leading intellectuals of the British Labour movement in the first half of the twentieth century, ranking with Harold Laski and R.H. Tawney. Through his enormous output of books, articles and pamphlets, he became one of the best-known socialists in the world. He wrote A History of Socialist Thought in the final years of his life; the first volume appeared in 1953 and the last posthumously in 1960. It had been substantially completed, and was prepared for publication by Cole's wife, Margaret Cole, with the help of Julius Braunthal and Humphrey Cole. The five volumes (two of them double volumes) comprised over 3,000 pages of text, and were a remarkable achievement, which Cole himself never expected to live to complete. He had been in poor health ever since diabetes was diagnosed in 1931 and his condition worsened in the 1950s.

His original intention had been to write simply a history of socialist thought and not a history of the socialist movement, but although this worked well for the first two volumes, which deal with the early socialists and with Marx and Bakunin, Cole found that in the later periods he could not disentangle the two, and expanded the book to include a detailed history of how socialism developed as a political movement through the insurrections of 1848, the founding of the First International, the Paris Commune, the Second International, the Russian Revolution and the struggle against fascism. He concluded his History in 1939, although in his final volume he often refers to post-1945 developments.

Cole's History covers the period between 1789 and 1939, but the bulk of it is focused on the ‘Socialist century’ inaugurated by the events of 1848. This was the period when socialism, having been associated with a few isolated thinkers and groups, grew into a worldwide movement which transformed politics and political debate. Cole was an active participant in the later stages of this history, and an original contributor to socialist political thought in his own right, as one of the chief theorists of guild socialism. His History is remarkable for its detail and its encyclopaedic knowledge as well as for its lucidity.