In a recent report, Jennifer Kavanagh of Defense Priorities called for the U.S. to end its formal security commitments to Japan, South Korea, and the Philippines and to withdraw nearly all of its forces in those countries to the Second Island Chain. This shift, Kavanagh argues, would leave the U.S. “more secure” with a “more sustainable military footprint.”
The report deserves credit for diversifying debate in Washington. However, we disagree with Kavanagh’s recommendations. A Second Island Chain strategy would not protect vital U.S. interests or enhance regional stability. U.S. regional dominance, as the report identifies, is no longer possible or necessary, but withdrawing to the Second Island Chain risks destabilizing the region and undermining Washington’s hand in any future conflicts in East Asia.
The geopolitical dimension
The report assumes that after terminating its alliances with Japan, South Korea, and the Philippines, the U.S. could still preserve enough influence in Asia to maintain a balance of power not dominated by China; even without U.S. defense commitments, these allies could not only defend themselves militarily against China but could also retain sufficient political autonomy.
Yet China need not achieve regional dominance through military conquest to render these states exceedingly vulnerable to coercion. Indeed, China can pursue sustained coercion by exploiting economic dependencies or using gray-zone military activities to punish Japan, South Korea, and the Philippines for refusing to accommodate its interests, incentivizing them to bandwagon with China rather than balance against it. Without the U.S. as a credible guarantor for these states’ security, China could, for instance, pressure countries to accommodate its positions in territorial disputes or limit cooperation with the U.S. in strategically important industries like semiconductors and shipbuilding.
U.S. defense commitments in East Asia do not prevent China from engaging in aggressive gray-zone coercion against U.S. allies, as in the South China Sea, but they do raise the costs to China of crossing certain escalatory thresholds. A binding U.S. security guarantee, combined with a credible military deterrent, is an essential backstop to ensure both Chinese and allied activities remain bounded by an appropriate understanding of risk. Without U.S. commitments, China would face far fewer risks in using escalation coercively. Contrary to the report's claims, informal security partnerships and a residual U.S. presence would not provide effective assurances against this risk of coercion.
In light of that reality, it is quite possible that South Korea and Japan would pursue nuclear weapons. Kavanagh acknowledges the risk of regional nuclear proliferation but understates both the likelihood and the dangers associated with it.
In South Korea, there is widespread public support — 76%, as of May 2025 — for an indigenous nuclear deterrent. Though South Korean policymakers are more cautious, a 2024 study found that the majority of South Korean strategic elites who oppose nuclearization would shift their support in favor if Washington terminated its alliance with Seoul. In Japan, despite a strong taboo against nuclear weapons, studies have similarly shown how that reservation erodes when respondents are presented with a world in which the U.S. no longer guarantees Japanese security.
The South Korean and Japanese pursuit of nuclear weapons could plunge East Asia into conflict. Indeed, China and North Korea would face a strong temptation to preempt South Korean or Japanese nuclear development with military force, despite the associated risks. North Korea, in particular, would treat South Korea’s nuclear acquisition as an existential crisis, facing the potential loss of its only military advantage over the South. Japan faces similar risks; China’s insecurity about Japanese rearmament is deep-rooted.
If a conflict were to erupt in Asia, the U.S. could not simply ignore it, even if Washington chose not to intervene militarily. The war would have a direct and severe negative impact on vital U.S. interests, particularly economic ones. Japan and South Korea are the world’s 4th and 12th largest economies and the 6th and 7th largest U.S. trading partners, respectively. Sixty percent of all global trade passes through Asian waters. Bloomberg Economics found that a Second Korean War would cost the world economy 3.9% of GDP — and shrink U.S. GDP by 2.3% — in its first year.
It is unclear why the U.S. would willingly fuel these dangers when the consequences are so severe and, ultimately, avoidable. China does have strong economic and political incentives to pursue stability rather than disruption. But basing U.S. access to the world’s most important region on the hope that Chinese intentions remain status-quo oriented is not a prudent management of risk.
The military dimension
Kavanagh argues that two U.S. interests necessitate a continued but minimal U.S. military presence in East Asia: preventing an attack against the U.S. homeland and maintaining access to the region’s economic markets and trade routes. By Kavanagh’s own definition, therefore, the U.S. should act in some cases against possible Chinese military use in East Asia. The problem, however, is that in the event of a U.S.-China conflict, the U.S. could not secure access to the western Pacific with the majority of its forces deployed to the Second Island Chain rather than the First.
The U.S. must maintain peacetime access to ensure wartime access. Withdrawal would force the U.S. to fight two battles: the fight for access and the conflict itself. Militarily, therefore, no alternative exists to a First Island Chain-centered defense strategy. This holds for two different scenarios: a Chinese amphibious assault and a sea denial campaign.
Why is this the case?
First, China’s land-based anti-access/area-denial capabilities are extensive. Those capabilities are designed specifically to counter U.S. power projection in the region. U.S. forces are most vulnerable when they are massed and operating in the open — easy targets for China’s long-range, precision-strike missiles, which can reach well into the Second Island Chain. Defending against a Chinese amphibious assault in the First Island Chain from the Second would require U.S. forces to surge forward across thousands of miles of exposed, open ocean for weeks at a time.
Second, the U.S. lacks the required sealift to rapidly move the bulk of its combat power forward in a conflict. A 2019 Department of Defense exercise found that only about 40% of U.S. sealift was ready for immediate use in a crisis. Similarly, Adm. Samuel Paparo, head of U.S. Pacific Command, has said his command’s Combat Logistics Force, which includes sea and airlift, only meets 60% of current operational requirements.
Third, China possesses the world’s largest navy by hull count, and it is becoming increasingly proficient at operating its fleet at sea for weeks at a time, including in the Second Island Chain. The U.S. can no longer assume, as Kavanagh appears to do, that it will enjoy an uncontested command of the sea. Instead, the U.S. and China will compete intensely for sea control. In the event of a Chinese sea denial campaign, withdrawing to the Second Island Chain would put the U.S. at a severe operational disadvantage. It would make it far easier for China’s surface ships — nearly all of which are armed with anti-ship missiles — and submarines to prevent the U.S. from gaining access to and operating in the western Pacific. Any plausible effort to re-secure trade routes would require, at minimum, a months-long naval campaign with a level of attrition unseen since the Second World War.
Willingly choosing to respond to a conflict from the Second Island Chain would thus provide China an extraordinary advantage. Five thousand U.S. forces in Japan, which Kavanagh would like to reduce even further by 2035, would serve as little more than a speedbump. China would begin a conflict on third base, while the U.S. would be forced to sit at first and fight its way to second. A Second Island Chain strategy would therefore not reduce U.S. forces’ vulnerability or casualties; it would likely increase both, and unnecessarily.
Of course, Kavanagh bases part of her argument on the assumption that reductions in U.S. forces in the First Island Chain will obviate the very reason for their use by reducing Chinese threat perceptions and thus the risk of an unnecessary war. Yet that assumption is misplaced. Changes to U.S. and Chinese force posture in the region are not the primary source of tension between the two countries; rather, their political differences are. Military tensions are simply a byproduct of that competition. It is thus unlikely that withdrawing to the Second Island Chain would fundamentally mitigate U.S.-China hostility. As made clear above, a Second Island Chain strategy would not serve as a sufficient hedge if assumptions about moderate Chinese intent proved inaccurate.
None of this means that the U.S. should continue on its current policy course in East Asia. Its relationship with China requires delicate diplomatic management, and cooperation should be pursued where possible. The U.S. should seek healthy competition, not one of unnecessary hostility. As recent research has called for, Washington should work to achieve constructive strategic stability with Beijing.
Further, while a First Island Chain defense strategy enables intervention to defend Taiwan, it does not necessitate it. Formal U.S. treaty allies should remain the principal focus of U.S. defense efforts. Making that clear would go a long way in helping reduce U.S.-China tensions. Ultimately, the U.S. needs a First Island Chain strategy that combines a calibrated approach to deterrence with proactive diplomacy to defend and advance its interests in East Asia.