Why, despite the territorial fragmentation and unresolved conflicts in both countries, does NATO maintain a public commitment to a 2008 decision promising the future membership of Ukraine and Georgia? It can be argued that the "Bucharest decision" has prompted the very attack that NATO membership was meant to prevent. Russia has invaded both states to, among other things, prevent their likely incorporation in NATO. What causes publicly articulated military alliance policy aspirations to endure when they induce such geopolitical conflict, and geopolitical transformation, that it undermines their purpose? This dissertation takes these puzzles as its object of inquiry. The focus of the study is Ukraine and Georgia's partial integration into NATO from 2007 to 2020. This research uses the concepts of robust action and rhetorical action to examine the two countries' growing partnerships with the alliance during this period. It defines robust action as a series of ambiguous moves to achieve tactical goals while maintaining long term flexibility. Rhetorical action is defined as the strategic use of arguments to serve an agent's interests. By using a narrative analysis method, the study draws from a body of NATO official texts and speeches and a set of original interviews to illustrate the public and private narratives used by political and military officials to help them make sense of NATO's engagement with Ukraine and Georgia. Existing literature on NATO expansion has not addressed how the alliance has adapted the process of integrating aspirant countries short of membership. Moreover, the literature on robust action has not focused on how international security organizations like NATO can use ambiguous actions to tackle complex challenges and maintain flexibility. The study argues that NATO's engagement with Ukraine and Georgia since Bucharest constitutes a robust action strategy. Through a combination of rhetorical and material support, NATO has simultaneously been able to maintain the appearance of a commitment to the two countries, show Western resolve and solidarity in opposing Russia and sustaining the United States' preferred vision of Europe's security order, all while denying Ukraine and Georgia "full membership" in the alliance. Ukraine, Georgia, and their allies in NATO have used rhetorical action, arguments based on the self-defined liberal values and norms of the Euro-Atlantic community that NATO represents on the one hand, and the historical precedent of an open door policy toward membership, on the other, to rhetorically entrap NATO into staying committed. The study shows how multilateral commitments are more layered than the traditional membership/no membership choice and how NATO has been able to successfully maintain such a commitment through both rhetoric and action while avoiding a direct war with Russia. It concludes however that NATO's commitment is untenable for a military alliance based on defense and deterrence. This has implications for the future of NATO expansion and the overall trajectory of the alliance. / Doctor of Philosophy / The possibility of further expanding NATO to Ukraine and Georgia has been among the alliance's greatest challenges since the 2008 Bucharest summit decision, which promised the future membership of the two countries. Many accounts tend to focus on the original motivation behind the decision rather than NATO's practice of maintaining a commitment to such a decision in the light of the unresolved conflicts and territorial fragmentation of both states. This study, by contrast, examines the rhetoric and action in the making of the two countries' deepening partnerships with NATO since Bucharest. This research examines how through a set of ambiguous rhetoric and action NATO has been able to maintain the appearance of a commitment to Ukraine and Georgia, project Western resolve against Russian opposition, and sustain the United States' preferred vision of the European security order, all while denying the two countries membership in the alliance. Moreover, the advocates for Ukraine and Georgia use arguments based on NATO's identity, values, and the precedent of prior expansions to convince the alliance into staying committed to their eventual membership. The study shows how NATO has devised a formula for integrating aspirant members, short of "full membership." It is useful because it shows how, in practice, multilateral commitments are more layered than they are traditionally understood. While NATO has been able to successfully maintain this commitment through both rhetoric and action, such a commitment clashes with important qualities of adaptability and flexibility to changing strategic realities, crucial to the endurance of a military alliance over the long term.