The United Socialist Movement (USM) was an anarcho-communist political organisation based in Glasgow. Founded in 1934 after splitting from the Anti-Parliamentary Communist Federation, the USM initially aimed to unite revolutionary socialists into an anti-fascist alliance and played a role in the early discussions on the founding of a "Fourth International". During the Spanish Civil War, it shifted its policies away from unconditional anti-fascism towards a revolutionary anti-militarism, which going into World War II led the USM into attempting to form a "Socialist-Pacifist alliance" and even collaborating with some reactionary elements in their opposition to the war. After the war, left with only a small old guard of anarchists and anti-parliamentarists, the USM again shifted its focus towards abstentionism, running unsuccessfully in a number of elections before its eventual dissolution in 1965.
