Abstract Important French foreign policy dyads, such as relations between France and the United Kingdom and France and the United States, have consistently been subject to empirical, historical and policy analysis. However, France's relationship with the broader Anglosphere is rarely considered or conceptualized. This article theorizes France's relationship with the Anglosphere at a pivotal historical juncture. The 2021 announcement of AUKUS, a security partnership between Australia, the UK and the US, spectacularly excluded France despite a shared proclivity to use military force in defence of liberal international order. To analyse this vital contemporary case, we undertake a comparative, computer-aided discourse analysis of 540 political and media texts, triangulated with thematic analysis of 37 elite interviews. First, contributing to constructivist and ontological security theory, we develop a novel theorization of alliance politics, generally, through the concept of ‘brOthers in arms’, whereby a double identity inscription binds allies antagonistically together. Second, contributing to critical studies of foreign policy and research on national identity, we locate France–Anglosphere relations, specifically, towards the thick end of an alliance identity spectrum, held together in mutual alterity by complementary, competing and co-constitutive exceptionalisms. Third, contributing to studies of foreign policy and alliance politics, our analysis situates AUKUS within the fractious longue durée of France–Anglosphere relations.