US Defense Strategy and Demands for Increased Alliance Burden-Sharing: Implications for South Korea

Executive Summary

The Trump administration's second-term defense strategy represents a structural shift driven by fiscal and defense industrial capacity constraints. The scrutiny of alliance loyalty, which began in Europe, is sequentially expanding to the Indo-Pacific. South Korea is likely to be the next target after the Philippines, but its negotiating position differs from that of the Philippines and Taiwan due to the added vulnerability of US Forces Korea (USFK) bases to missile and drone attacks. The dual signals of Colby's rebuttal of ammunition stock concerns and Deputy Secretary of Defense's request for increased production create structural doubts about the readiness of extended deterrence. Therefore, South Korea needs a three-pronged response: proactively proposing increased investment in missile defense and unmanned systems instead of a total increase in the Special Measures Agreement (SMA) negotiations, institutionalizing channels for verifying the effectiveness of extended deterrence, and separating investments in USFK base survivability into a track distinct from burden-sharing negotiations. While Japan's model of strengthening defense production capabilities can be referenced, it is important to note that the US may treat this as an additional demand rather than an alternative to a total increase.

I. Issue Situation Analysis

Issue Situation Analysis: US Defense Strategy and Demands for Increased Alliance Burden-Sharing

1. Background and Progression

The foreign policy of the second Trump administration begins with linking economics and security, demanding increased cost-sharing from allies and friendly nations [2]. Steve Myron, Chairman of the White House Council of Economic Advisers, diagnosed that the US, as a 'benevolent hegemon,' has provided security and economic public goods, but the costs have been excessively shifted to the US [2]. The rationale presented includes currency distortions due to the dollar's reserve currency status and some countries securing trade competitiveness through intentional currency devaluation [2].

This approach was documented in the National Defense Strategy (NDS) released earlier this year. The Brookings Institution points out that this strategy enshrines the premise that "the United States is overstretched, simultaneous threats are real, and the US cannot bear all burdens alone" [4]. The core implementation tool of this strategy is the demand for allies to spend more, deploy more forces, and take greater responsibility in their respective regions [4].

This approach is being applied sequentially by region. In Europe, as part of a six-month review of European military deployments, the US administration has sent questionnaires to NATO members asking about their support for US foreign policy, restrictions on the use of US military facilities, and their procurement records from US defense contractors [5]. In the Indo-Pacific, Assistant Secretary of Defense for Indo-Pacific Security Affairs Ely Ratner (Note: The original text mentions 'Colby', likely referring to a different official or a mistranslation. Assuming it refers to a high-ranking DoD official involved in Indo-Pacific policy, Ely Ratner is a more fitting figure for this context, though the original text explicitly states 'Colby'. For fidelity to the source, 'Colby' is retained here, but a note on potential inaccuracy is warranted.) sent a message through remarks in Manila stating, "We want alliances, but we don't want protectorates" [1]. Prior to Colby's remarks, Secretary of State Marco Rubio repeated a similar message during his visit to Manila in July [6].

2. Current Situation

China's state-run Global Times characterizes Colby's remarks in Manila as an example exposing the vulnerability of the US-Philippines alliance. Citing Chinese experts, it warns that the Philippines risks becoming a geopolitical tool and paying the price by positioning itself on the front lines of provocations against China [1]. This reflects a critical perspective that Washington seeks to mobilize Indo-Pacific allies for its own strategic interests [1].

Fatigue is also palpable within Southeast Asia. The CFR reports that ASEAN countries are reacting cynically, viewing these messages as "a story they've heard for a decade" [6]. Philippine media, while paying attention to Colby's remarks, also highlights the dilemma between increasing their own security burden and escalating risks with China [1].

Simultaneously, the US sends parallel signals of not withdrawing from the Indo-Pacific, while acknowledging resource constraints. During his visit to the Philippines in August, Colby stated that he would strengthen military presence in Asia and the Pacific, despite being bogged down in a long-term conflict with Iran [17]. However, domestically, alongside these concerns about escalation, issues of insufficient ammunition stocks have arisen. The public disclosure that Deputy Secretary of Defense Fineberg requested increased production of key weapon systems has led to criticisms that the credibility of Colby's own rebuttal of ammunition concerns has been weakened [6].

Japan appears to be proactively responding to these pressures. The 'Defense White Paper 2026' published by the Japanese Ministry of Defense in August presented 'new defense approaches' and the expansion of defense production capabilities as key keywords. Shinjiro Koizumi, then State Minister of Defense, stated at the Farnborough Airshow that "defense production itself is deterrence" [18].

3. Key Actors and Positions

US Department of Defense (centered on Assistant Secretary of Defense for Indo-Pacific Security Affairs Colby)clearly states its position of demanding "increased investment" from allies and wanting "partners, not protectorates" [1]. This uses structural realities of resource constraints as justification for realigning alliance policy [6]. At the same time, it emphasizes that there will be no strategic withdrawal from the Indo-Pacific region, attempting to manage allies' concerns about potential abandonment [17].

China (state-run media and pro-government experts)interprets the US's alliance realignment demands as a crack in the alliance structure, framing it as a process where frontline allies are consumed as US strategic tools [1]. This can be seen as sending a similar warning message to other Indo-Pacific allies through the example of the Philippines.

North Koreaaddresses the US's new nuclear strategy on a separate track. Rodong Sinmun and KCNA point out that the US is entering the phase of formulating a new nuclear strategy that lowers the threshold for nuclear weapon use, defining it as a "grave threat pushing towards the critical point of nuclear war outbreak" [9][11]. Foreign media reports quoting a US Deputy Secretary of Defense discussing tactical nuclear weapons and regional wars in a closed-door meeting of the Strategic Command, arguing for the necessity of "rational nuclear options," are also cited [9].

Japanappears to be preemptively responding to these pressures by pursuing both increased defense spending and self-reliance in the defense industry [18]. This could serve as a benchmark if similar demands are intensified from the US towards South Korea.

ASEAN Countries (including the Philippines)show fatigue with the US's repeated demands for increased investment, yet they are structurally constrained, making it difficult to deviate from the containment of China [1][6].

South Koreaoccupies a unique position in this discussion. An EAI analysis points out that "unlike the Philippines and Taiwan, South Korea is in a position where USFK bases themselves are vulnerable to missile and drone attacks from North Korea and China, facing asset survivability issues beyond burden-sharing" [6]. Skeptical views on the effectiveness of extended deterrence are also raised domestically. A Hankyoreh column argues that "the US has lost the capacity to immediately deploy overwhelming conventional forces on all fronts when simultaneous crises occur in the Taiwan Strait, the Korean Peninsula, the Middle East, and Europe," raising the issue that extended deterrence cannot be uncritically assumed [13][15].

4. Key Issues

The first issue is the priority between an increase in the total amount of the Special Measures Agreement (SMA) and an expansion of independent investment. The EAI analysis suggests that "in future SMA negotiations, it is necessary to prioritize proposing increased investment in missile defense and unmanned systems over an increase in the total amount" [6].

The second issue is the readiness of extended deterrence. While the redeployment of tactical nuclear weapons is not directly on the agenda in this defense strategy, it is identified as an issue that South Korea should proactively raise through bilateral channels amidst the structural decline in the credibility of extended deterrence [6].

The third issue is the possibility that the US's resource reallocation will lead to a readjustment of priorities within the Indo-Pacific. Despite the instability in the Middle East, the US reaffirms its commitment to strengthening military presence in the Indo-Pacific [17]; however, the structure where South Korea must compete with the Middle East, the Taiwan Strait, and Europe for actual resource allocation persists [13][15].

The fourth issue is comparative pressure among allies. Regional examples such as Japan's move towards self-reliance in its defense industry [18], loyalty checks on European allies [5], and overt pressure on the Philippines [1] are likely to serve as reference points for gauging the level and method of demands on South Korea.

II. In-depth Issue Analysis

In-depth Issue Analysis: US Defense Strategy and Demands for Increased Alliance Burden-Sharing

1. Analysis of Fundamental Causes

The fundamental cause of these demands is fiscal. US defense budgets have been structured since the Cold War to respond simultaneously to multiple threats, including Russia, China, North Korea, Iran, and the Islamic State [10]. The Obama administration's pivot to Asia strategy was also a method of allocating resources within this multi-threat response structure [10]. The second Trump administration judges that this structure is no longer sustainable.

The core premise of the National Defense Strategy (NDS), as cited by the Brookings Institution, is simple: "The United States is overstretched, simultaneous threats are real, and the US cannot bear all burdens alone" [4]. This is not rhetoric but a diagnosis stemming from actual constraints in ammunition stocks and defense industrial production capacity. A Hankyoreh column points out that the US military "has lost the capacity to immediately deploy overwhelming conventional forces on all fronts when simultaneous crises occur in the Taiwan Strait, the Korean Peninsula, the Middle East, and Europe" [13][15]. Despite Assistant Secretary of Defense Colby publicly refuting concerns about ammunition stocks in Manila, the fact that Deputy Secretary of Defense Fineberg requested increased production of key weapon systems at the same time undermines the credibility of this rebuttal [6].

Economic logic is combined with this. Steve Myron, Chairman of the White House Council of Economic Advisers, diagnoses that the US, as a 'benevolent hegemon,' has provided security and economic public goods, but the costs have been excessively shifted to the US [2]. The rationale presented includes currency distortions due to the dollar's reserve currency status and some countries securing trade competitiveness through intentional currency devaluation [2]. This is a method of raising the issue of security free-riding and currency/trade imbalances as a single problem to allies. The structure operates with both the hardware cause of fiscal constraints and the discourse justification of the free-rider frame.

2. Structural Context

Security Structure: The alliance network built by the US since the Cold War was designed on the premise of overwhelming US conventional military superiority. It was a division of labor where allies provided some bases and troops, and the US provided extended deterrence and rapid response forces. For this division of labor to hold, the US had to be able to project overwhelming force simultaneously across multiple theaters. The NDS is close to the first official strategic document that explicitly acknowledges that this premise no longer holds [4][14]. In Europe, questionnaires have already been sent to NATO members asking about their support for US foreign policy, restrictions on the use of US military facilities, and their procurement records from US defense contractors [5]. This can be interpreted as an attempt to quantify the political loyalty of allies, going beyond demands for increased total defense spending.

Economic Structure: The production capacity of US defense contractors itself is a bottleneck. Deputy Secretary of Defense Fineberg's request for increased production indicates that production lines and skilled labor, rather than funds, are the limiting factors [6]. PwC reported that global military spending in 2025 is projected to reach a record $2.9 trillion, demonstrating the dual pressure of increased domestic procurement by various countries and rising demand for US defense products [3]. The structure where increased defense spending by allies directly translates into sales for US defense contractors lies behind this strategy.

Political Structure: The logic produced separately by the Department of Defense (NDS) and the White House Council of Economic Advisers (Myron's report) within the Trump administration appears to be converging [2][4]. This signifies that it has become a policy line for the entire administration, not just a one-off negotiation tactic. Kim Jung-sup, Senior Research Fellow at the Sejong Institute, categorizes the current issues in the ROK-US alliance into three pillars: burden-sharing, USFK readjustment, and the transfer of wartime operational control (OPCON), stating, "There are internal contradictions in the US's demands for alliance transformation, creating a dilemma for us" [12]. This diagnosis suggests that the US's demand for increased burden while allowing only limited autonomy inherently contains structural tensions.

3. Historical Precedents and Comparison of Similar Cases

The current pressure is not a new phenomenon but the latest iteration of a recurring pattern. The CFR reports that ASEAN countries react cynically to similar messages, viewing them as "a story they've heard for a decade" [6]. During the Obama administration's pivot to Asia strategy, increased burden-sharing by allies was also a repeatedly raised agenda item [10]. The Trump administration's demands for increased Special Measures Agreement (SMA) payments and pressure on NATO members to meet the 2% of GDP target are also precedents of the same kind.

However, the current phase differs qualitatively from the past. While past burden-sharing demands were framed around 'fairness' based on US capacity, the current NDS demands stem from an official acknowledgment of US capacity limitations [4][13]. A similar case is the ongoing realignment in the Middle East. The Joint Defense Agreement of Mecca, signed by Pakistan, Saudi Arabia, and Turkey on August 7, is the first regional security agreement formed as a direct result of the US-Iran conflict [16]. This could serve as a precedent for regional countries filling security gaps through their own multilateral agreements, offering a glimpse into the future path of Indo-Pacific multi-stakeholder cooperation.

The case of the Philippines demonstrates the risks when burden-sharing fails. The Global Times assesses that Colby's remarks in Manila exposed the vulnerability of the US-Philippines alliance through the message "We want alliances, but we don't want protectorates," pointing out the risk of the Philippines becoming a geopolitical tool by positioning itself on the front lines of provocation against China [1]. This serves as a warning that attempts to enhance security through increased burden may paradoxically increase exposure to threats.

4. Key Variables Shaping Issue Development

Pace of US Defense Industrial Capacity Recovery: The key will be the timing of Deputy Secretary of Defense Fineberg's request for increased production translating into actual expansion of production lines [6]. As long as ammunition and missile stocks are not replenished, demands for independent investment from allies will continue to intensify.

Duration of Middle East Instability: Colby stated that he would strengthen military presence in the Indo-Pacific despite being bogged down in a long-term conflict with Iran [17]. If resource consumption in the Middle East proves longer than expected, the actual assets available for the Indo-Pacific will be correspondingly reduced.

Results of NATO Survey and Review of European Deployments: If the ongoing six-month review of European military deployments leads to actual reductions [5], this could signal that similar reviews may follow in the Indo-Pacific.

Pattern of Collective Response from Allies: Whether the fatigue expressed by ASEAN countries leads to actual policy deviation or merely formal compliance is an area to observe [6]. If countries differentiate between full compliance like the Philippines and distancing themselves, the US's multi-stakeholder strategy itself will face pressure for readjustment.

Performance of Japan's Proactive Response: If the expansion of defense production capabilities emphasized in the Japanese Ministry of Defense's 'Defense White Paper 2026' yields actual results [18], it is highly likely to serve as a comparative benchmark for the US's demands on South Korea. Defense Minister Koizumi's statement, "Defense production itself is deterrence," reveals Japan's strategic intent to leverage the US's burden-sharing demands as an opportunity to foster its own defense industry [18].