The 1940 split in the SWP was centered on the question of the party's internal regime but involved a series of other questions such as the class nature of the Russian state and Marxist philosophy. The minority faction led by Shachtman formed the Workers Party. In many ways the subsequent history of the party can best be assesed through the many splits and factional struggles, or lack of such struggles, that have marked the organisation.
During World War II, a number of members were imprisoned under the Smith Act of 1941 including JP Cannon. However the party put into practice the so called American Military Policy of opposing the war politically while arguing that their members of military age, which meant most of the membership, should go with their class into the military and attempt to transform the imperialist war into a civil war while fighting the Nazis.
Following the war the SWP and the FI both expected that there would be a wave of revolutionary struggles such as acompanied the end of the previous war. Thios however failed to materialise despite an increase in the level of labour strikes in the USA between 1945 and 1948 with the end of the wartime pledge made by many unions not to strike for the duration.
The end of the war also saw the reorganisation of the FI in which process the SWP played a major role. As part of this process moves were made to heal the breach with Max Shachtmans supporters in the Workers Party (WP) and for the tweo groups to fuse. This eventually came to nothing. However some members of the SWP around Felix Morrow and Goldman grew dissatisfied with what they saw as the SWP's ultra leftist attitude towards revolutionary policies and argued for the use of transitional politics as outlined by Trotsky in the Transitional Program which had been adopted by the FI in 1938. Eventually they were to leave the SWP in a state of demoralisation and some joined the WP.
On the other hand a faction within the WP called the Johnson-Forrest tendency, CLR James being Johnson and Raya Dunayevskaja Forrest, were impatient of the caution of the WP and considered that the situation could rapidly become pre-revolutionary. This led them to decamp from the WP and rejoin the SWP in 1947. This despite however having moved further away from 'orthodox trotskyism' than the SWP, for example they helkd that the USSR was a state capitalist society. by 1951 their presence in the SWP was ever more anomalous and most left in 1951. They would form the News and letyters Committees in 1955 after splitting with CLR James who was deported from the USA.
The party has also had a number of splits over the years. One such post war split saw the departure of the Pabloite faction of Cochran and Clarke who formed the Socialist Union which lasted until 1959. This 1953 opposition supported the positions of Michel Pablo the Secretary of the Fourth International. The next split was that of Sam Marcy's Global Class War faction which had called within the SWP for support of Henry Wallace's Progressive Party Presidential run in 1948 and was very supportive of the Chinese revolution. However they only left the SWP in 1958 after suporting the suppression of the Hungarian Rising of 1956 contrary to the position held by most Trotskyist tendencies. They went on to form the Workers' World Party.
Meanwhile throughout the 1950s and into the 1960s the remaining membership of the SWP clung to its firmly held beliefs and grew older. Consequently the party membership shrank over these years from a post war high in 1948 until the tide began to turn in the early 1960s. The 1959 Revolution in Cuba however signalled a change in political direction for the SWP as it embarked on solidarity work through the Fair Play for Cuba committee. The result was a small accretion of youth to the party's ranks and in the same period long time SWP leader Murray Weiss won another group of youth from the Shachtmanites as they joined the SPUSA.
Despite such growing signs of an end to the isolation which ther group had endured during the Macarthyite period it fell into a crisis in the early 1960s. This was in part because the leadership was unable to summon enough energy to satisfy the desire of the new younger members to engage in the Civil Rights struggles of thos years as their own view of class conflict had been shaped by the rise of the industrial unions in the 1930s and they saw everything through that prism. There was also an international aspect to this internal dispute as the SWP turned back to cooperation with the European based International Secretariat of the Fourth International. Those youth members who dissented with the conservatism of the leadership naturally looked for allies in the international movement of their own and found them in Gerry Healy's SLL which claimed a political orthodoxy that appealed to the Americans.
A factional situation developed in the SWP that saw a number of small oppositional groups develop. The most important however was the Revolutionary Tendency (RT) led by James Robertson, and Wohlforth. A split developed within this grouping however between groups headed by the two men. Nonetheless both the RT and the Reorganised Minority Tendency were expelled to form the Spartacist (see Spartacist League), and the American Committee for the Fourth International (see Socialist Equality Party)), respectively. In the aftermath the Seattle branch also left to found the Freedom Socialist Party, after protesting about the suppression of internal democracy, as did Murray and Myra Tanner Weiss.
Like all left wing groups the SWP grew during the 1960s and experienced a particularly brisk growth in the first years of the 1970s. Much of this was due to its central involvement in many of the campaigns against the war in Vietnam. However it was also increasingly strident in its defence of the Cuban regime of Fidel Castro and its identification with that regime. A new leadership led by Jack Barnes made this identification with Cuba an ever greater part of the politics of the SWP as throughout the 1970s. Initially this was partially concealed by the 'orthodox Trotskyist' positions that older members of the party developed in the pages of the groups publications. Particularly prominent in such writing was Joe Hansen who edited the groups international bulletin which to many was the voice of the SWP. Another activity that the group was responsible for through their publishing house Pathfinder Books was the publication in these years of many of Leon Trotsky's works. Not only were the better know writings reprinted, many for the first time since the 1930s, but other more obscure articles and letters were collected and printed for a wider audience than they had when first distributed.
The growth of labour militancy in the early 1970s had an impact on the SWP and currents developed within it urging a reorientation of the party towards this militancy. One such current was the Proletarian Orientation Tendency. Under pressure from the party leadership it dissolved itself however. But another similar tendency developed called the Internationalist Tendency (IT). The IT posed a greater challenge for the groups leadership however as it espoused the ideas of the European based leadership of the International Secretariat of the Fourth International. However, despite tensions between the SWP and ISFI, when the former expelled the IT the latter refused to defend their allies. The IT would disintegrate over the next few months some of its supporters finding their way back into the SWP.
This period was the peak of the SWP's growth and influence. None the less growth had stalled in the late 1970s and the organisation was at an impasse. Despite which the leadership, now based around a group formed around the figure of Jack Barnes many recruited at Oberlin college in the early 1960s, decided that the key task was for a turn to industry. This turn entailed party members getting jobs in blue collar industries in preparation for the coming mass struggles which Barnes argued were coming. The result was the movement of many members and their systematic uprooting often out of establushed careers and into low paying jobs in small towns. Many of the older members with experience in trade unions resisted this 'colonization program' as did younger members. In the meantime the group began to lose members.
The result of this process and the leadership's increasingly rigid disciplinery arrangements was the development of opposition within the group. This opposition was not homogenous and was itself beset my differences between different factions. On the one hand a group gathered around the Weinsteins on the West Coast, although they had supporters elsewhere too, while a second group gathered around George Breitman and Frank Lovell. Togther they formed an opposition bloc on the SWP's National Commitee but in 1983 the Barnes led leadership purged anyone not pledging support of the leadership. Those purged included almost every member of the SWP older than Barnes himself and has therefore been called the Age Purge it led to the SWP membership declining by a third.
Those purged swiftly regrouped and formed a number of groups. The grouping around the Weinsteins forming the San Francisco based Socialist Action group. Other oppositionists formed the Fourth International tendency which set itself the task of recapturing the SWP for their understanding of Trotskyism. However they soon lost a small group who constituted themselves as the Fourth International Caucus of the new 'regroupment' project Solidarity. The FIT continued to direct its work towards the SWP for many years until they finally recognised the impossibility of their task and dissolved into Solidarity. Their journal Bulletin in Defense of Marxism was to continue as Labor Standard. Meanwhile the other fragment of the SWP in Socialist Action continued losing a number of supporters around Alan Benjamin who formed the Socialist Organiser group in Solidarity with Pierre Lambert's international tendency. More recently they have broken into two groups one continuing as Socialist Action the other taking the name of the Socialist Workers Organisation which publishs a magazine called Socialist Viewpoint.
The party has run candidates for President since 1948; it received its greatest number of votes in 1976, when its candidate, Peter Camejo, received 90,310 votes. In 1976, the party won a lawsuit against the FBI as a result of years of spying by the FBI. During the 1970s and 1980s, the party abandoned Trotskyism in favor of a pro-Castro ideology. The party now has few members.
Since the 1970s, the National Secretary of the Socialist Workers Party has been Jack Barnes.