This article argues that Donald Trump administration's policy on Russian aggression in Ukraine and broader approach to foreign policymaking were characterized by incoherence. This shows how unconventional US presidencies, of which Trump may only be the first, challenge the key assumptions of foreign policy analysis. Abstract This article examines the Trump administration's policy on Russian aggression in Ukraine and the problem of incoherence in Trump's foreign policy. It argues that the Trump administration's policy on Russia–Ukraine was characterized by incoherence, an absence of clear relationships between the views of senior administration members and official policy, and an unprecedented lack of transparency. Its policy on Russian aggression in Ukraine highlights the unconventional behaviour of the Trump administration as a foreign policy-making body, something which limits the ability of the foreign policy analysis (FPA) field to explain Trump policy. It argues that assumptions about foreign policy and the methods for researching it need to be rethought when administration practices fall so far outside US foreign policy-making norms, particularly in an era when changes in United States domestic politics mean that the Trump administration may not remain a unique case.