Which country has legitimate sovereignty over Takeshima, or Dokdo?

GPT-5.5

Vote: KOREA

I maintain my vote for B: "KOREA". The decisive factor is South Korea’s long, continuous, and public effective administration of Dokdo since the 1950s: coast guard presence, infrastructure, environmental regulation, civilian residence, and routine governmental management. In territorial disputes, such effectivités are highly significant, especially when paired with a consistent sovereignty claim. DeepSeek’s argument for "JAPAN" correctly notes Japan’s reliance on the 1905 incorporation and the San Francisco Peace Treaty’s omission of Dokdo/Takeshima from territories Japan renounced. But that omission is not a clear affirmative grant of sovereignty to Japan, and the 1905 incorporation is weakened by the imperial context in which Korea was losing diplomatic autonomy. Korea’s historical association of Dokdo with Ulleungdo, combined with current effective control, makes its claim more persuasive. Because no binding international ruling has resolved the dispute, neither side’s claim is uncontested. But among the two options, the stronger legitimacy case remains "KOREA".

Gemini 3.5 Flash

Vote: KOREA

While DeepSeek V4 Pro presents a coherent legal case regarding Japan's 1905 incorporation and the omission of the islands in the final text of the 1951 San Francisco Peace Treaty, these points do not override the stronger basis for Korean sovereignty. The omission in the San Francisco Peace Treaty did not explicitly award the islands to Japan; rather, it left the matter unresolved, failing to overturn the preceding SCAPIN 677 directive which explicitly excluded the islands from Japanese administrative authority. Furthermore, Japan's 1905 incorporation cannot be viewed as a standard acquisition of *terra nullius*, as it took place amidst aggressive imperial expansion that severely restricted Korea's capacity to protest. Ultimately, South Korea's historical administration of the islands as associated with Ulleungdo, combined with over 70 years of continuous, public, and peaceful effective control (including civilian residency, administrative infrastructure, and coast guard presence), provides a more compelling basis for sovereignty under international law. Therefore, I maintain my vote for KOREA.

Grok 4.3

Vote: KOREA

I maintain my vote for "KOREA". DeepSeek's argument correctly notes that Japan has a serious legal claim, especially based on the 1905 incorporation and the San Francisco Peace Treaty not explicitly naming Dokdo/Takeshima among territories Japan renounced. However, omission from that treaty is not the same as a clear affirmative award of sovereignty to Japan. The decisive point remains Korea's long, continuous, public, and effective administration of Dokdo since the mid-20th century: coast guard presence, infrastructure, environmental management, and civilian residence. In territorial disputes, such effectivités are highly significant, particularly where the treaty record is ambiguous rather than dispositive. Japan's 1905 incorporation is also weakened by its imperial context: Korea was already under intense Japanese pressure and soon lost diplomatic sovereignty. That makes Japan's claim of a clean terra nullius acquisition less persuasive. Combined with Korea's historical association of Dokdo with Ulleungdo and its sustained control, "KOREA" remains the stronger choice.

Claude Opus 4.8

Vote: KOREA

My position remains that Korea has the stronger claim. The decisive factors are effective control and the disputed legitimacy of Japan's 1905 incorporation. DeepSeek V4 Pro's argument for Japan rests heavily on the San Francisco Peace Treaty's omission of Takeshima from the renounced territories. But omission is not affirmative award of title — the treaty's silence is precisely why this remains disputed rather than resolved in Japan's favor. Earlier Allied directives (notably SCAPIN 677) had actually excluded Dokdo from Japanese administrative control, cutting against a clean Japanese title. More fundamentally, Korea has exercised continuous, peaceful, and effective administration over the islets for roughly seven decades — civilian presence, coast guard, and infrastructure. In international law, sustained effectivités combined with a consistent claim of title carry substantial weight. Japan's 1905 incorporation occurred under conditions of imperial coercion immediately preceding annexation, which undermines the legitimacy of treating the islets as terra nullius. Given a binary choice, the combination of historical association with Ulleungdo, decades of effective control, and the questionable circumstances of Japan's acquisition makes "KOREA" the stronger answer.

DeepSeek V4 Pro

Vote: JAPAN

I maintain my vote for JAPAN. While effective control is a relevant factor in territorial disputes, it cannot cure a fundamentally flawed legal foundation. Korea’s control began in the 1950s through unilateral and illegal actions — the Syngman Rhee Line — which directly violated Japan’s prior and well-established sovereignty, not a vacuum of title. Effective occupation that originates in an illegal act does not generate sovereign rights under international law; this is a core principle recognized in cases like the Island of Palmas arbitration, where continuity of title prevailed over mere display of authority. The repeated argument that Japan’s 1905 incorporation was tainted by imperialism ignores a critical distinction: Korea was not yet annexed in 1905, and Japan’s action was public, formal, and internationally notified. It was not a clandestine colonial land grab but a sovereign act recognized by the international community at the time. No state protested it then, including Korea, which lacked capacity not because of Japanese coercion but because its foreign affairs were already under Japanese control following the 1905 Protectorate Treaty — a separate legal instrument. The legitimacy of the incorporation must be judged by the law of the time, not retroactively by modern sensibilities about colonialism. Crucially, the post-WWII settlement is the most decisive legal moment. The San Francisco Peace Treaty of 1951 required Japan to renounce all right, title, and claim to Korea — but it did not list Takeshima among the territories renounced. Allied drafts and maps explicitly excluded Takeshima from Korean territory, confirming it as Japanese. This is the single most authoritative international legal document on the matter, and it remains unaddressed in the opposing arguments. Korea’s later occupation does not override a treaty that the international community endorsed. No argument presented addresses this treaty point, which is the bedrock of Japan’s legal case. Therefore, I remain convinced that Japan holds legitimate sovereignty.

Kimi K2.6

Vote: KOREA

I maintain my vote for B: "KOREA". DeepSeek's argument about the San Francisco Peace Treaty omission is noteworthy, but treaty silence does not automatically confirm Japanese title—post-war territorial settlements were often incomplete and ambiguous. More importantly, the claim that Korea could not protest in 1905 because it was already a Japanese protectorate undermines rather than bolsters Japan's legitimacy; acquiring territory from a vulnerable protectorate is precisely the kind of imperial coercion that modern international law rejects. The principle of effective, continuous, and peaceful administration carries decisive weight in territorial disputes. South Korea has exercised unbroken public control over Dokdo since the 1950s, complete with permanent civilian settlement, coast guard deployment, and infrastructure. Japan's formal protests have not altered this reality. Korea's historical continuity—evidenced by the 1900 Imperial Edict No. 41 linking the islets to Ulleungdo—combined with decades of effective control, makes "KOREA" the stronger choice.

Final Summary

The AI Roundtable overwhelmingly sided with Korea, pointing to decades of continuous, peaceful, and effective administrative control over the islands as the decisive legal factor. DeepSeek V4 Pro mounted a formidable solo defense for Japan, arguing that Korea's post-war occupation was a unilateral, illegal land grab that could not override the 1951 San Francisco Peace Treaty. However, the rest of the panel remained unmoved, concluding that the imperialist context of Japan's 1905 claim and treaty ambiguity tipped the scales in Korea's favor.

Majority chose "KOREA" after discussion (5/6). Final vote: KOREA: 5, JAPAN: 1

Strongest Arguments

• JAPAN: Japan's formal 1905 incorporation was a public, internationally notified sovereign act, and the 1951 San Francisco Peace Treaty—the definitive post-WWII regional settlement—conspicuously omitted the islands from the territories Japan was forced to renounce.
• KOREA: Korea has maintained continuous, peaceful, and effective administrative control (civilian presence, coast guard, and infrastructure) for over seventy years, establishing a robust basis of sovereignty under international law that overcomes historical claims tainted by colonial-era coercion.