This paper investigates the arguments used in public documents to mobilise Bulgarians against the deportation of Jews in World War II. We focus on the key documents relating to the first wave of mobilisation in 1940–1941 as provided by Todorov in The Fragility of Goodness (2001). We demonstrate that these documents are based on three types of argument. The first, category inclusion, treats the Jews as part of a common ingroup rather than as constituting a separate outgroup. The second, category norms, proposes that help for those under attack is a core aspect of ingroup identity. The third, category interest, suggests that the ingroup will be harmed if Jews are persecuted. In each case, the predominant category on which arguments are based is national identity (i.e. ‘we Bulgarians …’). This analysis is used to validate and extend a social identity of model of helping. The theoretical and practical implications of such an approach are considered in the discussion. Copyright © 2006 John Wiley & Sons, Ltd.