As part of a larger study of the Cold War in Australia, this article examines the anti-communist crusade waged by the RSL, 1946-50. As distinct from agencies of the state, the RSL was a large, influential, voluntary organisation which played a significant role in the development of the Cold War. The first section of the article is essentially a detailed narrative of the implementation of a policy of purging the membership of the League of suspected communists. Then an account is provided of the wider aspects of the campaign to eliminate all influences of the Communist Party. In the final section, an attempt is made from several different approaches to explain the crusade and the intensity of its prosecution. No simple answer emerges, but the exploration reveals further essential components of the development of the Cold War in Australia.