Even after the demise of its territorial caliphate in 2019, ISIS persists as a potent threat, adapting to new technologies and maintaining its status as an active insurgency. Amidst the backdrop of the terror group’s demonstrated resilience, this paper examines its practice of (de)legitimation and language of persuasion through a multimodal argumentation analysis. It combines the argumentation strategies (topoi) proposed by Discourse-Historical Approach (DHA) and tools from Social Semiotics with argumentation theories, achieved through a comprehensive enthymematic deconstruction of arguments in ISIS’s e-magazine, Dabiq. The findings reveal four interrelated sets of plausibly inferable premises, namely, advantage and disadvantage; threat and obligation; negative consequence and history; and authority and Shariah law. These premises fall within broad social, political, historical, and religious categories and are deliberately crafted to lend support to ISIS’s desired conclusions, aimed at systematically altering the addressees’ state of knowledge and eventually eliciting acceptance from the intended public.