<p>Why do great powers sometimes provide a partner with too little security assistance to deter a rival, instead of sending costly arms or allying? Existing explanations argue that great powers limit their assistance to avoid entrapment. I argue that they balance two considerations when deciding on the form of security cooperation: first, whether it will deter or provoke the external rival, and second, whether to use security cooperation to pursue deterrence or to maintain or extend regional order. When great powers fear provocation and are primarily interested in order making rather than deterrence, they are more likely to choose forms of security assistance that do not significantly alter the military balance. I build this theory through a case study of US security cooperation with Ukraine between 2014 and 2022. I conclude by discussing implications for contemporary US policy toward Taiwan.</p>