Opinion – Alliance Shock Revisited: What 1968-69 Means for 2025

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In January 1968, North Korean special forces penetrated the very heart of Seoul in order to assassinate South Korean president Park Chung-hee. The operation, which came alarmingly close to achieving its objective, sent shockwaves throughout South Korea’s leadership, showcasing that South Korea’s internal security was still vulnerable, even after the Korean Armistice was signed in 1953. Barely one year later, another strategic shock hit in a completely different manner. With the election of Richard Nixon, the US’ Asia strategy was fundamentally readjusted: it demanded that US allies assume greater responsibilities when it came to defending themselves. The aforementioned two incidents — the Blue House raid and the Guam Doctrine — were merged into a single perception for both Japan and South Korea: that US protection cannot be considered as automatic while regional survival would be more dependent on self-reliance and cooperation between Japan and South Korea.

After more than half a century, Japan and South Korea are facing structural unpredictability that strongly reminds us of 1968-69. Donald Trump’s return to the White House revived transactional alliance politics, again amplifying the issue of burden-sharing. At the same time, North Korea has evolved into a full-blown nuclear power, China is testing the threshold of coercion in the Taiwan Strait, and the deepening of military cooperation between Russia and North Korea is adding another unstable axis in Northeast Asia. As such risk elements overlap with one another, it is creating a denser, riskier strategic environment than the Cold War era when the Guam Doctrine was declared. Nevertheless, the strategic logic that Tokyo and Seoul are faced with is strikingly similar. Once again, they must determine whether to remain as passive dependents on the alliance or evolve into a common supplier of regional security. The consequences of this choice in 2025 will have far more decisive implications than the choices that were made in 1969. Yet, in order to grasp today’s dilemma, it is essential to review the initial inflection point. In the late 1960s, Japan and South Korea both experienced the abrupt rupture of strategic clarity. The Blue House raid shattered any remaining belief that South Korea could fully rely on outsiders. North Korea was no longer a conventional threat confined across the DMZ and had proven its ability to directly project asymmetric violence against South Korea’s political core.

Such shock was amplified by the Guam Doctrine. Although it did not formally announce US troop withdrawal from Asia, the doctrine did clearly demonstrate the denouement of an era where US commitments were nearly automatic. Such an implication was grave in a country where the trauma —the US decision to exclude South Korea from its defense perimeter in early 1950 — was still deeply imprinted on the South Korean psyche. It was equally destabilizing to Japan, where its security was buttressed through the 1947 Peace Constitution and US extended deterrence. Although Japan’s reaction was restrained, it was a historically important turning point. In November 1969, Japanese prime minister Sato Eisaku officially announced that South Korea’s security was essential for Japan’s own security, implicitly redefining the Korean Peninsula as Japan’s defense perimeter. This statement marked a conceptual transformation from distancing in the post-war era, to strategic interdependence. Despite the fact that defense cooperation in an institutional sense was under political constraint, it showcased that the strategic perception itself was already shifting.

Nevertheless, the most notable result of this first shock was materialized not through troop dispatch or command integration, but through industrial strategy. Based on the 1965 Japan-South Korea normalization treaty, Japan was to provide $300 million in grants and $200 million in long-term, low-interest loans as a claims fund. Despite the nationwide opposition from the South Korean public, the Park Chung-hee administration redirected this fund towards full-fledged heavy industrialization. At the core of such a decision lies the construction of the Pohang steel mill, which became South Korea’s first integrated steel mill, thanks to Japanese loans, technological assistance, and international financing. With the passage of time, the Pohang steel mill was established as the backbone of South Korea’s modern defense industry since South Korea’s shipbuilding industry, armored vehicle production, artillery system, and ammunition manufacturing capability could not have been developed without domestic steel production. Under US strategic uncertainty and North Korea’s conventional military threat, Tokyo and Seoul inadvertently transformed a politically explosive reparation settlement into a long-term security asset. What was initiated as economic cooperation shifted into enhanced deterrence through greater industrial capability. This case displays the in-depth reality of alliance politics. Security is not ensured only through treaty and troop deployment. It is supplemented by manufacturing capability, technological maturity, and supply chain flexibility.

Such historical logic is urgently resurfacing under a far riskier environment. Unlike in 1968, North Korea is not constrained by penetration operations and provocations using conventional arms. North Korea has ICBMs, tactical nuclear systems, hypersonic missiles, and survivable launch platforms that enable an early use of nuclear weapons. The failure of deterrence is no longer an issue of invasion, but has turned into a nuclear coercion scenario in the early stages of a conflict. At the same time, China’s military posture against Taiwan transformed a once theoretical crisis scenario into a criterion for practical operational plans. A prolonged war in Taiwan could necessitate immediate and massive consumption of the US’ air, naval, cyber, and missile defense assets. Such a burden would directly resonate on the Korean Peninsula, and the North Korean leadership would have a strong incentive to test the alliance cohesiveness while the US focus was distracted. The deepening military cooperation between Moscow and Pyongyang has alleviated North Korea’s isolation and heightened the risk in the region by indoctrinating the Eurasian escalation logic into Northeast Asia.

Such trends have developed what defense planners describe as a dual contingency environment: a scenario where crises in the Taiwan Strait and the Korean Peninsula occur either simultaneously or in a sequential manner. Under such circumstances, the traditional alliance model, namely the US-led hub-and-spoke model, faces unprecedented strain. Such strain is being magnified under the second Trump administration, due to the return of conditionality. To be sure, Washington has not officially abandoned its defense commitment, but it is no longer automatically assumed by Tokyo and Seoul that Washington is willing to bear an unlimited burden for alliance defense. Once again, Japan and South Korea are faced with the strategic problem that first emerged in 1968 — anxiety about alliance abandonment — on how to manage but avoid overreaction. The institutional progress represented by the 2023 Camp David summit was an important initial response in institutionalizing intelligence sharing, joint exercises, and cooperation on deterrence among the US, Japan, and South Korea. However, the institutional structure alone cannot overcome the US’ material and political limits during a dual contingency scenario. Even the most advanced consultative mechanism cannot substitute practical capabilities of regional allies to absorb shocks, maintain combat capability, and prevent opportunistic aggression when Washington’s attention is diffused.

Here, the experience of 1969 is offering strategic lessons that could be applied in today’s world. The first lesson is the principle of indivisible security. As Sato acknowledged that the Korean Peninsula’s stability cannot be separated from Japan’s own safety, Tokyo and Seoul should accept that Taiwan and South Korea’s security are structurally interconnected with one another. A war in the Taiwan Strait would immediately threaten the Japanese territory and US bases, while creating incentives for North Korean adventurism. Meanwhile, the collapse of deterrence in the Korean Peninsula would destabilize the entire first island chain. Thus, treating these two crises as a separate alliance issue is no longer analytically nor operationally reasonable. Second most important is the central role of industrial capability when it comes to long-term deterrence. The Pohang steel mill was the strategic industrialization for the previous generation. Today, missile interception systems, precision guided munitions, unmanned systems, cyber infrastructure, AI-based C2 networks, and naval shipbuilding could be the equivalents. For Japan and South Korea to withstand protracted high-intensity warfare without unlimited and immediate US supply, it is necessary to establish joint production capacity and shared stockpiles that enable the two countries to preserve operations in multiple theaters.

The third lesson is the danger of overly asymmetric dependence. During the Cold War, Japan and South Korea both structurally relied on Washington, yet maintained very shallow levels of security cooperation with each other. Such structure delegated all major decisions to a single external hub, increasing crisis instability. Although today’s trilateral cooperation framework has markedly enhanced, bilateral security integration between Japan and South Korea has still not met the operational need. Independent consultation mechanisms, a permanent liaison structure, and institutionalized crisis management systems should complement — and not simply depend on — US-led processes if the alliance is to preserve its resilience. The fourth lesson is the division of labor when the US is overburdened. The Guam Doctrine did not mean US abandonment, but it made allies assume clear operational responsibility within the joint strategic framework. Amidst a dual contingency, Japan’s mission should be concentrating on rear area logistics, missile and anti-air defense, anti-submarine warfare, and maritime supply protection; South Korea’s priority will continue to be deterring North Korean invasion and safeguarding allies’ key infrastructure within the Korean Peninsula. Such division of labor does not aim to substitute US power, but acts as a multiplier that ensures efficiency under extreme pressure.

The last lesson is a political one. The 1965 claims fund and the redirection of funds in constructing Pohang steel mill succeeded domestically not because historical grievances were resolved but because it was legitimized as an instrument of national survival through development. Today, historical memory and identity politics are functioning as strong elements of constraining Japan-South Korean cooperation. Without a shared narrative that frames integration as a matter of collective survival under nuclear and great power threat, even the most strategically sound security initiative would be politically fragile. From the theoretical perspective, both 1969 and 2025 represent classic alliance-shock moments where threat component and patron reliability compel secondary states to rebalance. In the late 1960s, North Korea’s provocation coupled with US’ strategic withdrawal led to indirect consultation between Tokyo and Seoul through industrial strategy. In the 2020s, a similar pressure has emerged due to the rise of a three-adversary bloc — comprised of China, Russia, and North Korea — and US conditionality. The structural pressure is incentivizing Japan and South Korea to simultaneously pursue internal balancing as well as regional external balancing.

However, force alone does not determine the outcome. As Camp David has shown, institutional density lowers transaction costs and stabilizes strategic expectations. Meanwhile, what type of cooperation is politically viable would eventually be determined by domestic legitimacy. Japan-South Korea integration would not only advance thanks to strategic necessity but because leaders would provide a narrative—survival in a nuclearized Northeast Asia depends on deeper alignment—that could convince the public. The shock of 1968-69 forced Japan and South Korea to encounter the limits of automatic US protection and the risk of strategic negligence. Their responses, including industrial transformation, cautious coordination, and gradual defense autonomy, contributed to buttressing the stability of Northeast Asia during the latter years of the Cold War. Yet, today’s stake is much higher. Cyber warfare, hypersonic missiles, and the probability of a dual crisis both in the Taiwan Strait and in the Korean Peninsula have profoundly transformed the meaning of alliance dependence.

If Tokyo and Seoul fail to deepen strategic integration, both countries might repeat the pre-1968 illusion that regional security could unconditionally rely on a single external great power. On the contrary, if they succeed, the second ‘Guam moment’ could be transformed into a new era of shared deterrence. As Pohang’s furnaces once forged the material foundation of South Korean security, the choices that are made by Japan and South Korea will determine whether the next ten years will be split asunder due to dual contingency or will be integrated thanks to strategic maturity.