A certain amount of political disagreement and internal debate within the member states has always been part of EU (foreign and security) policy-making. Over the past few years, however, domestic actors have fundamentally challenged, undermined and even reversed established EU norms, policies, and procedures. Different political and societal actors – from political parties to civil society organisations – have been engaging in acts of internal contestation, both directly through government policies and indirectly by shaping the domestic debate. Whether different acts of contestation have been able to make a lasting impact on EU foreign and security policy capacity remains to be seen. On the one hand, contestation can simply result in a more pluralistic policy debate. On the other hand, member states’ stances on certain policy areas have become extremely polarised, with some capitals drastically changing their policy positions and challenging fundamental EU norms. This type of internal contestation has severely curtailed the Union’s ability to act promptly and effectively on the global stage.