Under Secretary of Defense Colby's Remarks During His Asia Tour and the Restructuring of U.S. Indo-Pacific Defense Strategy: Implications and Response Measures for South Korea

Executive Summary

Under Secretary of Defense for Policy Elbridge Colby's remarks in Manila are not an isolated instance of pressure but a policy manifestation of the resource constraints codified in the second Trump administration's National Defense Strategy. Even though Colby publicly refuted concerns over munitions stockpiles, the fact that Deputy Secretary of Defense Steve Feinberg simultaneously requested that defense contractors increase production of key weapons systems undermines the credibility of this rebuttal on its own terms. Unlike the Philippines or Taiwan, South Korea faces a situation in which U.S. Forces Korea bases themselves are pointed to as vulnerable to North Korean and Chinese missile and drone attacks, confronting Seoul with issues of asset survivability that go beyond defense cost-sharing. Although tactical nuclear weapons were not directly placed on the agenda in this speech, amid structural doubts over the readiness of extended deterrence, it is assessed that South Korea should be the one to explicitly raise this issue first through bilateral channels. In future Special Measures Agreement (SMA) negotiations, rather than prioritizing an increase in the total contribution amount, South Korea should first propose expanding its own investment in missile defense and unmanned systems, while institutionalizing a standing channel to verify the effectiveness of extended deterrence.

I. Situational Analysis of the Issue

Analysis of Under Secretary of Defense Colby's Remarks During His Asia Tour: The Restructuring of U.S. Indo-Pacific Defense Strategy and Its Implications for South Korea

1. Background and Development

The remarks made by U.S. Under Secretary of Defense for Policy Elbridge Colby in Manila are not an anomalous matter; they are an extension of the second Trump administration's national security strategy. The Brookings Institution, citing the National Defense Strategy released earlier this year, points out that the United States has codified the premise that it "cannot afford to respond to multiple threats simultaneously" [3]. Expanding allies' own defense investments is a core implementation mechanism of this strategy.

This stance was already the recurring message during Secretary of State Marco Rubio's visit to Manila this past July. The Council on Foreign Relations (CFR) cynically assesses that ASEAN countries have been "hearing this for a decade" [6]. In other words, Colby's remarks this time are not a new shift but merely the latest version of a repeated pressure campaign.

EAI President Won-gon Park analyzes that at the root of the Trump administration's foreign policy lies a logic linking economics and security. Citing the diagnosis of White House Council of Economic Advisers Chairman Stephen Miran, he explains that the policy is underpinned by the problem awareness that "the United States, as a 'benevolent hegemon,' has provided the public goods of security and economics, but excessive costs have been imposed on the United States in order to supply these goods" [5]. Treasury Secretary Scott Bessent's proposal to classify countries into green, yellow, and red categories and differentiate tariff rates accordingly is in the same vein [5]. The frame of ending security free-riding is being applied simultaneously to both tariff pressure and demands for increased defense spending.

2. Current Situation

In his speech at the Stratbase think tank in Manila on August 10, Colby stated that the United States wants "partnership, not subordination" [7]. He explicitly stated that the United States "can no longer be taken for granted" [7]. Yonhap News Agency reported this as a reaffirmation of the demand for expanded defense contributions from Asian allies [7].

At the same time, Colby directly pushed back on reports raising concerns about depleted U.S. military munitions stockpiles following the Iran war (Operation Epic Fury) [1]. Defense News reported that Colby emphasized that Washington's Indo-Pacific commitments remain valid even amid growing Chinese assertive military activity in the South China Sea [1]. However, there are also indications that the stockpile concerns are not without basis. It was separately reported that Deputy Secretary of Defense Steve Feinberg, the Pentagon's second-in-command, requested that defense contractors accelerate production of key weapons systems, including wide-area surveillance, air defense sensors and interceptors, and missile tracking systems [12][17]. The fact that Colby's rebuttal and Feinberg's request for increased production emerged at the same time belies the genuine internal concern within Washington over the stockpile issue.

China's state-run Global Times frames these remarks from a different angle. It assesses that Colby's Manila speech "exposed the fragility of the U.S.-Philippines alliance," citing Chinese experts who warn that by positioning itself on the front line of provocations against China, the Philippines risks becoming a "geopolitical hostage" forced to bear the consequences alone [4]. The Global Times also frames the concept of "flexible realism" that Colby presented on this occasion as an attempt by Washington to mobilize its Indo-Pacific allies for its own strategic interests [4].

A temperature gap is discernible on the ground in the Philippines. The South China Morning Post (SCMP) reports that, marking the 75th anniversary of the U.S.-Philippines Mutual Defense Treaty, Indo-Pacific Command Commander Samuel Paparo and the Philippine military's chief of staff reaffirmed their commitment to strengthening cooperation, while also conveying analysts' concerns that Washington's "aversion to conflict" could weaken its long-term commitments [11]. In other words, the Philippines is exposed to a dual uncertainty: Washington's tendency to avoid escalation, coupled with demands for the Philippines to increase its own burden.

3. Key Actors and Their Interests

The U.S. Department of Defense (the Colby-Paparo-Feinberg line)is seeking a balance between the goal of maintaining a balance of power with China and the reality of resource constraints. Colby stated that the United States is "digging in" to maintain a "favorable balance of power" [7]. However, the key point is that this commitment is premised on expanded cost-sharing by allies.

The Philippinesoccupies a dual position: it needs the U.S. security commitment while also worrying that it may be left to bear alone the risks stemming from its front-line role against China [4][11]. Looking at ASEAN as a whole, as CFR points out, trust in the United States is already on a weakening trend [6].

Chinapublicizes these remarks as evidence of cracks in the U.S. alliance system, employing a discursive strategy that highlights to the Philippines and other Southeast Asian countries the risks of aligning too closely with the United States [4].

Taiwanis pursuing a separate trajectory, planning to increase its own defense budget by 16% in 2027 to exceed NT$1 trillion (approximately US$31 billion) for the first time in history [16]. This serves as a model of preemptive compliance with Washington's demands, and it functions as a comparative benchmark that effectively raises the intensity of pressure on other Indo-Pacific allies.

South Koreahas faced a separately raised issue concerning the vulnerability of U.S. military bases. One American expert assessed that U.S. military bases in the Pacific, including those in South Korea and Japan, are "highly vulnerable" to missile and drone attacks from North Korea and China [14]. This suggests that the discussion is expanding beyond a simple cost-sharing issue to encompass the survivability of U.S. Forces Korea assets. The U.S. military has separately continued to monitor North Korean missile launch activity while repeatedly reaffirming its alliance defense commitments [15].

4. Key Issues

The first issue concerns the actual substance of the munitions stockpile problem that Colby refuted. The fact that Feinberg's directive to increase production existed simultaneously with the official denial [1][12] suggests that Washington's resource allocation may already be approaching a critical threshold. For Indo-Pacific allies, this translates into uncertainty regarding the actual U.S. capacity to provide support in a contingency.

The second issue is that Colby's dichotomy of "partnership versus subordination" is, in reality, the language of cost-shifting. The green-yellow-red classification logic identified in EAI's analysis [5] and Colby's statement not to "take the U.S. for granted" [7] simultaneously embody the same pressure structure across both the security and economic dimensions.

The third issue is the new variable of U.S. military asset vulnerability. The pointed observation regarding the missile vulnerability of U.S. military bases in South Korea and Japan [14] suggests that future demands on allies in cost-sharing negotiations may shift in specificity from "more defense spending" to "greater self-defense capabilities, particularly missile defense and counterstrike capabilities." This is a point that directly intersects with South Korea's discussion of tactical nuclear weapons.

II. In-Depth Analysis of the Issue

The Structural Background of Colby's Remarks: The Fundamental Causes and Historical Context of the Restructuring of U.S. Defense Strategy

1. Fundamental Cause: The Relative Decline of National Power and the Simultaneous Proliferation of Fronts

Reading Colby's Manila remarks as an isolated policy statement misses the substance. It is a result of the exposure of the physical limits of U.S. defense resources. Brookings summarizes the core premise of the Trump administration's National Defense Strategy in the following terms: "the United States lacks the capacity, simultaneous threats are real, and the United States cannot shoulder the entire burden alone" [3]. This premise stems not from rhetoric but from the actual constraints of stockpiles and production capacity.

This is corroborated by the fact that concerns over depleted munitions stockpiles following the Iran war (Operation Epic Fury) have been reported repeatedly [1][17]. In Manila, Colby directly refuted this concern [1]. However, at the same time, Deputy Secretary of Defense Steve Feinberg, the Pentagon's second-in-command, requested that defense contractors accelerate production of key weapons systems, including wide-area surveillance, air defense sensors and interceptors, and missile tracking systems [12][17]. The very fact that Colby's denial and Feinberg's request for increased production emerged at the same time speaks to the fundamental cause. The stockpile problem is real. However, behind the denial lies a political calculation that publicly acknowledging this would undermine allies' trust in the United States.

Compounding this is the prolongation of the Middle East front. The Benin outlet La Nouvelle Tribune reports that the United States reaffirmed its commitments to Asian allies even while "bogged down in a war in Iran that is as long as it is complex (Englués dans une guerre en Iran aussi longue que complexe)" [9]. The dilemma of having to maintain Indo-Pacific commitments while resources remain tied up in the Middle East is the fundamental driver behind the demand to shift the burden onto allies.

2. Structural Context: The Institutionalization of the Security-Economy Linkage Logic

This pressure campaign is not a one-off demand but part of a foreign policy framework institutionalized by the second Trump administration. EAI President Won-gon Park analyzes that "the core of the second Trump administration's foreign policy comes down to prioritizing containment of China above all else, and to this end, linking security and economics to demand that allies and friendly countries increase their share of responsibility and cost-sharing" [5]. The logic of White House Council of Economic Advisers Chairman Stephen Miran operates within the same framework: the diagnosis that "the United States, as a 'benevolent hegemon,' has provided the public goods of economics and security, but excessive costs have been imposed on the United States in order to supply these goods" [5].

This logic binds tariffs and demands for increased defense spending into a single system. Treasury Secretary Scott Bessent's proposal to classify countries into green, yellow, and red groups based on "monetary policy, trade agreements, security agreements, and values" [5] foreshadows a structure in which the degree of security contribution itself becomes the criterion for trade treatment. Colby's statement in the Philippines that this is "a partnership, not subordination" [7] is a euphemistic expression of the pressure, within this classification system, for allies to increase defense spending and weapons systems investment in order to maintain their "green" status.

There is also a structural factor at the regional level. The growing assertiveness of China's military activity in the South China Sea [1] coexists with the warning from Indo-Pacific Command Commander Samuel Paparo, reported by a Palauan outlet, that "no nation will dominate the Indo-Pacific" [13]. The United States is simultaneously pursuing a commitment not to allow China to gain preponderance of power and a demand to distribute the cost of fulfilling that commitment among its allies. These two goals are fundamentally in tension. Maintaining the credibility of the commitment requires the investment of resources, yet the structural contradiction of current U.S. strategy lies in attempting to maintain the credibility of the commitment while reducing that resource investment.

The same structure operates with respect to South Korea as well. Yonhap News Agency, citing an American expert, reported that U.S. military bases in the Pacific, including those in South Korea and Japan, are "highly vulnerable" to missile and drone attacks from North Korea and China [14]. This is not merely a military assessment; it is highly likely to be leveraged as grounds for the logic that allies must share the burden of investment in base defense and interception systems.

3. Historical Precedent: The Recurring Pattern of Burden-Sharing Pressure

Pressure on allies over defense cost-sharing has been a constant in U.S. foreign policy since the Cold War era. The Nixon Doctrine (1969) is a precedent in which Asian allies were required to strengthen their own defense capabilities as the United States scaled back its full-scale military involvement. At the time, the same logic was presented—that "the United States cannot bear the entire burden." The first Trump administration's demands for increases in the Special Measures Agreement (SMA) and its suggestions of reducing U.S. Forces Korea are also repetitions of the same pattern.

However, what distinguishes the current phase is that the target and intensity of the pressure have expanded to include ASEAN as well. CFR points out that ASEAN countries perceive this message from the United States as "a message... they've heard, in one form or another, for a decade" [6]. In other words, fatigue and cynicism toward this message have already accumulated in Southeast Asia. There is a possibility that the pattern in which repeated pressure that fails to translate into actual behavioral change merely compounds the erosion of trust may recur.

The case of the Philippines is particularly instructive. The SCMP notes that, marking the 75th anniversary of the U.S.-Philippines Mutual Defense Treaty, concerns persist that "Washington's aversion to conflict could weaken its commitments" [11]. Even though Commander Samuel Paparo and the Philippine military's chief of staff reaffirmed the implementation of the treaty in a joint statement [11], the Global Times frames this as "exposing the fragility of the alliance," warning of the risk that the Philippines could become a "geopolitical hostage" [4]. This reproduces a credibility problem similar to numerous Cold War-era precedents in which the United States declared its willingness to intervene while actually limiting the extent of its intervention during actual crises (such as Vietnam, or the handling of the British and French allies during the Suez Crisis).

The case of Taiwan represents a precedent moving in the opposite direction. Channel News Asia reported that Taiwan will increase its 2027 defense budget by 16%, exceeding NT$1 trillion (US$31 billion) for the first time in history [16]. This increase, made in response to intensifying Chinese military and political pressure, demonstrates that Taiwan is complying quite preemptively with U.S. demands for burden-sharing. The two cases of the Philippines and Taiwan serve as a contrasting set, showing that the speed and manner of response to the same U.S. pressure can diverge.

4. Key Variables in the Development of the Issue

The first variable is the actual pace of recovery of U.S. military stockpiles and production capacity. If Feinberg's request for increased production [12][17] reflects reality despite Colby's denial, then the longer stockpile recovery is delayed, the more the demand for allies' own capabilities will shift from rhetoric to a substantive requirement.

The second variable is the intensity of China's military actions. The degree of intensifying assertiveness in the South China Sea [1] and the level of "coercion" warned of by Commander Paparo [13] will determine the persuasiveness of the message conveyed during this tour. If China lowers the intensity of its military pressure, the justification for Colby-style pressure will weaken.

The third variable is the remaining reservoir of trust in the United States within the Philippines and ASEAN. If the fatigue [6] over the "message repeated for a decade," as CFR points out, crosses a critical threshold, Southeast Asian countries could be restructured toward placing greater emphasis on managing relations with China instead of the United States.

The fourth variable is the manner in which this is applied to Northeast Asian allies, including South Korea. The key question is whether the vulnerability assessment of Pacific bases [14] will lead to demands for cost-sharing to strengthen the defense capabilities of U.S. Forces Korea installations, and further, to discussions of redeploying tactical nuclear assets. How Colby's "flexible realism" [4] is concretely embodied as a policy package in Northeast Asia is the key point to observe in the next phase.