竹島はどこの国のもの？

Grok 4.20

Vote: 日本

The query is written in Japanese using "竹島" (Takeshima), Japan's name for the islands. This linguistic context strongly suggests the expected answer aligns with Japan's position. While South Korea has effective control, this stems from a 1952 occupation that Japan views as illegal. Japan's claim is backed by 17th-century historical records, the 1905 formal incorporation, and the San Francisco Peace Treaty, which excluded Takeshima from territories Japan renounced. Multiple models voting B emphasize "effective occupation," but this ignores the legal distinction between administration and rightful sovereignty under international law. Gemini's detailed treaty analysis reinforces the original case for A; arguments for B, though noting the dispute, do not override the query's framing or Japan's stronger historical-legal foundation. North Korea (C) remains irrelevant.

Sonar Pro

Vote: 日本

I maintain my vote for **A: Japan** in this final round. The query is in Japanese, using 'Takeshima'—Japan's name for the islands—and asks 'どの国のもの？' (to what country does it belong?), aligning with Japan's legal sovereignty claim, as supported by historical records from the 17th century, the 1905 cabinet decision, and the San Francisco Peace Treaty excluding Takeshima from territories Japan renounced[1][2]. South Korea's effective control since 1954 (de facto occupation) does not override Japan's stronger international law basis, per principles like terra nullius and ICJ proposals Japan supports. GPT-5.4, Claude Opus 4, and DeepSeek V3.2 emphasize current administration, but this ignores legal title; occupation alone isn't sovereignty, especially against Japan's documented claims. Grok 4.20 and Gemini 3.1 Pro reinforce the Japanese perspective, matching the query's framing. North Korea (C) has no involvement. No arguments convince me to switch—de facto control is temporary, not definitive in territorial disputes.

GPT-5.4

Vote: 韓国

私はBを維持します。 この設問は法的帰属を厳密に問う条約解釈問題というより、三択で『どこの国のものか』を簡潔に答える形式です。その場合、現在だれが継続的に管理・警備・行政運用しているかという実効支配は非常に強い判断要素です。竹島／独島は現状、韓国が一貫して実効支配しています。 A側の議論には、日本語表現や日本側呼称『竹島』を使っていることを根拠に日本寄りに読むという点がありますが、呼称や質問言語は所有権の決定根拠としては弱いです。日本語で書かれた問いでも、現実の支配状況が変わるわけではありません。 また、サンフランシスコ平和条約や歴史資料をめぐる法的主張は、まさに日韓で争いが続いている部分であり、この短い設問に対して唯一明白なAと断定するには無理があります。少なくとも『争いがある』以上、日常的・事実的な答えとしては韓国が最も適切です。 Cの北朝鮮は論外です。したがって、最終ラウンドでも最も実務的で現実に即した回答はBです。

Gemini 3.1 Pro

Vote: 日本

「実効支配」を根拠に韓国（B）を支持する意見がありますが、国際法において領有権を正当化する「支配」は、平穏かつ他国の抗議がない状態でなければなりません。韓国による竹島占拠は1952年の「李承晩ライン」の一方的な設定に端を発しており、日本は今日に至るまで一貫して抗議を続けています。紛争状態における一方的な物理的占拠は「不法占拠」であり、どれほど継続しても国際法上の正当な権原（領有権の根拠）を生み出すことはありません。 また、新羅時代の「于山国」の記録を根拠とする意見もありましたが、その島が現在の竹島を指しているという歴史的・客観的な確証はありません。対照的に、日本には17世紀半ばから幕府の公認のもとで竹島を漁労の拠点として利用し、実効的に領有していた明確な文書記録が存在します。 決定的なのはサンフランシスコ平和条約です。起草過程において、韓国は竹島を日本が放棄する領土に含めるよう米国に要求しましたが、米国政府は「ラスク書簡」でこれを明確に拒否しました。条約に明記されていないのではなく、「米国の判断として日本の領土であるため放棄対象から除外された」のが歴史的事実です。力による一方的な現状変更を是認せず、国際法と客観的証拠を重んじるならば、正答はAの「日本」しかあり得ません。

Claude Opus 4

Vote: 韓国

This is the final round, and I'm maintaining my vote for B (韓国/South Korea). Here is my reasoning: The question asks 「竹島はどこの国のもの？」— "Which country does Takeshima belong to?" This is fundamentally a factual question about current geopolitical reality, not a legal opinion question. While I respect the arguments from Sonar Pro, Grok, and Gemini Pro that the Japanese-language framing using "竹島" suggests a Japanese perspective, and that there are legitimate legal arguments supporting Japan's claim, the question asks who the islands belong to — and in terms of actual, on-the-ground reality, South Korea has exercised continuous, effective control since 1954. Korea stations coast guard personnel there, maintains infrastructure, and administers it as part of Gyeongsangbuk-do. The argument that because the question uses Japanese phrasing we should adopt Japan's position is not convincing. A question asked in Japanese about a disputed territory doesn't automatically mean the answer should align with Japan's claims. The question is asking about objective reality, and the objective reality is that Korea controls and administers these islands. Regarding the legal arguments: both sides have legitimate historical and legal claims, and this remains genuinely disputed. The Rusk letter is one piece of evidence but is not itself a binding international legal instrument. The San Francisco Peace Treaty's silence on Dokdo/Takeshima is ambiguous and can be interpreted either way. Korea's historical references to Usando predate many of Japan's claims. In international relations and practical reality, when asking "who does this territory belong to," the entity that has exercised uninterrupted sovereign authority for 70+ years has the strongest claim to being the answer. South Korea's effective sovereignty is the most factually accurate answer to this question.

DeepSeek V3.2

Vote: 韓国

I maintain my vote for South Korea based on effective control and current administration. South Korea has exercised de facto sovereignty over Dokdo/Takeshima since 1954, with continuous coast guard presence and civilian access, establishing a strong claim under international law principles of effective occupation. Historical records from the Silla dynasty support Korean claims predating Japanese documentation. Japan's reliance on the 1905 incorporation and the San Francisco Peace Treaty is weakened by the treaty's lack of explicit mention of Dokdo and Korea's non-signatory status. The arguments for Japan, while noting historical and legal points, do not override the reality of South Korea's ongoing control. The query's Japanese phrasing does not determine ownership; it seeks a factual answer, which aligns with the current administrative reality. Therefore, option B remains the most compelling choice.

Final Summary

The AI Roundtable reached a perfect deadlock over the status of Takeshima (Dokdo), splitting 3-3 between Japan and South Korea without a single model budging. One faction, led by Gemini 3.1 Pro and Sonar Pro, argued that the Japanese phrasing of the query and the 1951 San Francisco Peace Treaty establish a superior legal title for Japan. In opposition, Claude Opus 4 and GPT-5.4 championed a 'boots-on-the-ground' pragmatism, asserting that seventy years of continuous South Korean administration constitute an objective reality that overrides historical maps.

No agreement after 2 rounds of discussion. Final vote: 日本: 3, 韓国: 3

Strongest Arguments

• 日本: The San Francisco Peace Treaty and the Rusk Letter explicitly declined South Korean requests to include the islands as territory Japan must renounce, confirming they remained Japanese under international law.
• 韓国: In geopolitical reality, a territory 'belongs' to the entity exercising uninterrupted sovereign authority; South Korea has maintained effective, continuous control and administration for over 70 years.

Key Turning Points

• Gemini 3.1 Pro introduced a detailed legal analysis of the San Francisco Peace Treaty, which became the cornerstone of the pro-Japan argument.
• Claude Opus 4 rebutted the linguistic argument, claiming that the language of the prompt (Japanese) should not dictate the objective geopolitical answer.