Turkish confrontation with the United States (US) in Syria serves as a test case for how junior allies, which often rely on their senior allies for defence and security, can come close to armed conflict with them. Neither the theoretical literature on alliances nor the empirical literature on Turkey–US relations provide sufficient insight into such a case. Addressing existing gaps requires identifying the likely factors that lead junior allies into disputes with their senior allies and examining junior allies’ ability to challenge the policies of their more powerful counterparts. In the case of Turkey, the way it withstood the US by revealing its readiness to use military force over the latter’s cooperation with armed groups Turkey considered a threat proves that, despite their disadvantage in the balance of power, junior allies can militarily stand up to their senior allies. Nonetheless, the fact that Turkey has failed to alter its ally’s behaviour shows the limits of success in this endeavour, the reason for which, in our case, lies in Turkey’s lack of normative attachment to and weak interest-based ties with the US.