References to the rules-based order are frequent in everything from the Biden-era Interim National Security Strategic Guidance to the Trump-era Advantage at Sea. Yet what it means to defend the order, where that defense happens, and what those answers hold for questions of budgets and priorities, is often ambiguous. How should diplomats and operational forces bridge the gap between high-level pronouncements on the rules-based order and practical guidance and budgeting for the daily defense of that order? The development of the new National Security Strategy and National Defense Strategy offers two venues to address that question. And the answers should focus not strictly on any one adversary, but on a series of domains: the global common—the high Arctic, the high seas, and space.