Discussions about U.S. military posture in the Indo-Pacific often assume that the United States will have the ability to not only quickly access its military capabilities stationed in the region, but also to freely operate from bases in allied countries. The authors of this report explore this assumption, examining the opportunities and constraints that the U.S. military might face when operating from the territories of Japan, the Republic of Korea (ROK), and the Philippines. The authors examine the basing and access assumptions for the U.S. military should it wish to preposition supplies in, and operate from, these allies in peacetime and in a conflict over Taiwan when these allies themselves have not been attacked. For this research, the authors conducted a comprehensive literature review of historical and current studies on access; held an internal RAND workshop with military experts to determine the types of capabilities and access requests the United States might make of Japan, the ROK, and the Philippines in a Taiwan contingency; conducted extensive discussions and interviews in the fall of 2022 with officials and experts in Japan, the ROK, and the Philippines and with U.S. government personnel and experts in the United States who work on issues related to these three allies; and examined important agreements the United States has with each treaty ally that are relevant for U.S. military access and basing. The authors present their findings regarding access and basing for each ally and recommend ways to improve outcomes in both areas.

A substantial divide has developed between the United States and China since 2017, largely driven by both nations' fundamentally different, and perhaps irreconcilable, objectives and priorities. While conflict is possible, it is also unlikely, as leaders in both countries desperately want to avoid war. The more likely future for US-China relations is one involving heightened economic and technological competition, ongoing regional tension as China continues to coerce its neighbours, and increasing pessimism in both Washington and Beijing about their ability to deter and counter each other. In this environment, meaningful cooperation and improved relations will be improbable.

Ensuring military access to the territory of allies and partners in the Indo-Pacific in the event of a future conflict with China is a critical concern for U.S. policymakers. The physical and political geography of the region sharply limits U.S. options to such an extent that some allied and partner decisions to provide or refuse access could determine the outcome of a conflict. A clearer understanding of how and why U.S. allies and partners are likely to make conflict-phase access decisions, and what U.S. policymakers can do to affect the decisions ahead of time, is therefore essential. In this report, the authors examine how U.S. allies and partners make conflict-phase access decisions and how the United States and the U.S. Air Force (USAF) might be able to influence decisions in advance. The authors developed a framework for assessing such decisionmaking, then applied it to five specific allies and partners in the region (Japan, the Philippines, Singapore, Indonesia, and India) to assess their strategic outlooks, internal politics, and economic incentives and to identify the peacetime policy levers that are most promising for affecting the states' decisionmaking.