James P Cannon's father was an Irish Republican and pioneer socialist living in Kansas, USA. Cannon himself (1890-1974) started work in a factory at the age of 12, joined the Socialist Party at 16, and then became an organiser for the Industrial Workers of the World (IWW), a revolutionary trade union movement in the USA at the time which mainly organised transient workers.
After the Russian Revolution of 1917, Cannon rejoined the Socialist Party and became a leader of its pro-Bolshevik left wing and then of the Communist Party of the USA (CPUSA).
Over 10,000 suspected US communists were arrested, many deported, and some killed, in the "Palmer Raids" between 1918 and 1921. Cannon's first big battle inside the CPUSA was to get the party to go into legal politics after the repression relaxed. After that the CPUSA was still torn by internal faction-rights, and paid little attention to the remote-seeming battle between Stalin and Trotsky in the USA. Cannon led one faction, whose main work was the International Labour Defence campaign in support of the USA's many class-war prisoners.
Then, as a delegate to the Communist International's World Congress in 1928, Cannon by chance came across a document from Trotsky. He was convinced. On his return to the USA, he spoke out for Trotsky - which earned him expulsion from the CP, the sack from his job as a party organiser, being cut off by most of his friends, and physical attacks by CPers on the meetings of the Trotskyist group which Cannon and his comrades organised, the Communist League of America (CLA).
The CLA went through years of extreme political isolation from 1928 to 1933, but gained strength from 1934 onwards. By 1939, renamed the Socialist Workers Party (SWP - no relation to the modern SWP-UK), it was the most solid of the world's small Trotskyist organisations.
In 1940 the SWP split over attitudes to the USSR's invasions of Poland (September 1939) and Finland (winter 1939-40). Cannon (supported by Trotsky) argued that, while the invasions could not be supported, the overriding consideration was "defence of the USSR". A minority led by Max Shachtman and others argued that the invasions were plainly imperialist.
The SWP-USA, unlike Trotskyist groups in continental Europe, was able to operate more or less legally during World War Two; but in 1941, Cannon and a number of other SWPers and sympathetic trade unionists were indicted for "conspiring to overthrow the US government". Cannon was jailed from 1943 to 1945.
After 1945 Cannon was the acknowledged veteran leader of "orthodox Trotskyism" worldwide. But he was hesitant about many of the ideas developed by the theoreticians of this "orthodox Trotskyism", such as Michel Pablo and Ernest Mandel, and in 1953 he led a split which divided "orthodox Trotskyism" into two currents on an international level, one (Cannon's) more anti-Stalinist than the other.
From 1953 Cannon was semi-retired, but intervened from time to time, within the framework of "orthodox Trotskyism", to try to rebuke the veerings towards Stalinism inbuilt in that framework and to hold back the SWP leaders from disciplinary tightening-up which he reckoned would "strangle the party". After the death of Cannon and some of his close associates, the SWP-USA degenerated very quickly into a sect which strongly supports the dictatorships in North Korea and Cuba.
