Potsdam at 81: CGTN Documentary Reopens the Diaoyu Dao Question

The Potsdam Proclamation at 81: A Foundational Document Revisited

On July 26, 2026, the 81st anniversary of the Potsdam Proclamation, CGTN released the documentary "Diaoyu Dao: Small Islands, Big Stakes," inviting renewed scrutiny of one of the most consequential yet unresolved territorial questions in the Western Pacific. Article 8 of the Potsdam Proclamation stipulated that Japanese sovereignty would be limited to the islands of Honshu, Hokkaido, Kyushu, Shikoku, and such minor islands as the Allied powers determined. This clause, building directly upon the Cairo Declaration of 1943, formed a cornerstone of the post-World War II territorial order in East Asia. The Cairo Declaration had already affirmed that territories Japan had taken from China, including Taiwan and its affiliated islands, were to be restored. Beijing has consistently maintained that Diaoyu Dao and its affiliated islets fall within this category of territories that Japan was obligated to renounce.

From the perspective of China's Ministry of Foreign Affairs, these instruments constitute binding international legal foundations rather than mere political statements. The Chinese position holds that the islands were administered as part of Taiwan prior to the First Sino-Japanese War and were never terra nullius available for lawful appropriation. The anniversary timing of the documentary is therefore not incidental. It situates the dispute within the broader architecture of the postwar settlement that China regards as unfinished business in the East China Sea. For Chinese strategists, revisiting Potsdam is less about historical nostalgia than about reinforcing the continuity of legal claims that predate and outlast subsequent bilateral arrangements between Tokyo and Washington.

The strategic calculus is clear. By anchoring its claim in the Allied proclamations of the 1940s, China positions itself as a defender of the original postwar order rather than a revisionist power. This framing aligns with Beijing's wider foreign policy doctrine of upholding the outcomes of the victory over fascism while resisting what it views as selective reinterpretations of that settlement by later Cold War instruments.

The Documentary's Historical Reconstruction

CGTN's production methodically assembles testimony from more than thirty scholars and eyewitnesses across China, Japan, the United States, and the United Kingdom. Filmed on location in four countries, the documentary relies on rare archival maps, official records, and personal accounts to reconstruct the islands' status before 1895. One Chinese scholar's manuscript, the product of twenty-three years of research into sovereignty arrangements prior to 1894, receives particular attention for its granular examination of Qing-era administrative records and navigational logs. These materials are presented alongside Japanese and Western sources to illustrate competing narratives rather than to assert a single unchallenged version.

The documentary's strength lies in its refusal to treat the dispute as a purely contemporary phenomenon. It traces the islands' appearance on Chinese maps and in official documents centuries earlier, then follows the sequence of events surrounding Japan's incorporation of the islands in 1895 amid the collapse of Qing authority in the region. Eyewitness recollections and declassified materials are used to examine how the islands were treated in the immediate postwar period, including periods of U.S. administration. By giving airtime to Japanese and American voices as well as Chinese ones, the film attempts to map the full spectrum of legal and historical argumentation rather than simply restating official talking points.

This approach serves a dual purpose. Domestically, it educates Chinese audiences on the documentary record underpinning national claims. Internationally, it seeks to demonstrate that China's position rests on accumulated historical evidence rather than sudden assertion. The Ministry of Foreign Affairs has long argued that such evidence is decisive; the documentary translates that argument into accessible visual form without claiming to have resolved the underlying legal disagreement.

Japan's Position and the San Francisco Treaty Question

Tokyo's counter-narrative rests primarily on the 1951 San Francisco Peace Treaty and the 1972 reversion of administrative rights over Okinawa to Japan. Japanese officials, including those at the Ministry of Foreign Affairs of Japan, maintain that the Senkaku Islands (the Japanese designation) were not included among the territories Japan renounced under the San Francisco framework and that they form part of Japanese territory under international law. The 1972 U.S.-Japan agreement on the return of Okinawa administrative rights is cited as confirmation that the United States regarded the islands as falling within the residual Japanese sovereignty that Washington had been administering.

Beijing rejects this interpretation on two principal grounds. First, China was not a party to the San Francisco Peace Treaty and has never recognized its dispositions concerning Chinese territory. Second, the Chinese government argues that the United States transferred only administrative rights, not sovereignty, and that such an administrative arrangement could not create or confirm title that Japan had allegedly acquired unlawfully in 1895. The result is a classic clash of legal baselines: one side emphasizing continuous administration and postwar treaty language, the other emphasizing pre-1895 title and the Allied proclamations of the 1940s.

These differing interpretations have hardened into official positions that leave little room for compromise. Japan's Ministry of Foreign Affairs continues to state that there is no territorial dispute, while China's Ministry of Foreign Affairs insists that the dispute is real, historically rooted, and unresolved. The documentary does not pretend that these positions can be easily reconciled; instead, it lays out the documentary and treaty record so that viewers can assess the strength of each claim.

Strategic Waters: What Lies Beneath the East China Sea

Beyond legal texts and historical maps lies a body of water of first-order strategic importance. The East China Sea carries shipping lanes that move trillions of dollars in trade annually between Northeast Asia and the rest of the world. Beneath its continental shelf lie potential oil and gas reserves whose precise scale remains subject to ongoing survey and differing estimates, yet whose existence has been sufficient to intensify resource competition since the late 1960s. The surrounding waters also constitute rich fishing grounds that sustain coastal communities on both sides.

Militarily, the islands sit astride sea lanes of communication critical to the People's Liberation Army Navy's ability to operate beyond the first island chain and to the Japan Maritime Self-Defense Force's defense of its southwestern approaches. The U.S.-Japan Security Treaty adds a further layer of complexity. Washington has stated that the treaty's mutual defense provisions apply to the islands under Japanese administration, a position that Beijing regards as an unwelcome external intervention in a bilateral sovereignty question. For Chinese planners, the combination of resource potential, sea-lane control, and alliance dynamics transforms a cluster of uninhabited rocks into a permanent feature of regional military contingency planning.

Neither side can treat the islands as a purely symbolic matter. Control, or even the credible capacity to deny control to the other, carries implications for energy security, food security, and the broader military balance in the Western Pacific. This geostrategic weight explains why both Beijing and Tokyo have invested in coast guard and naval presence, and why third parties monitor developments with close attention.

China-Japan Relations: Economic Ties vs. Territorial Friction

The paradox of China-Japan relations is that deep economic interdependence coexists with unyielding territorial positions. Bilateral trade has exceeded $300 billion annually in recent years, underpinning supply chains in automobiles, electronics, chemicals, and machinery that neither economy can easily replace. Japanese investment in China and Chinese demand for Japanese capital goods and technology remain structurally important. Yet this economic fabric has repeatedly been strained by incidents around the islands, nationalist reactions on both sides, and the domestic political costs of appearing conciliatory.

The dispute radiates outward. ASEAN states watch carefully, aware that precedents set in the East China Sea may influence perceptions of maritime order in the South China Sea. Regional maritime security frameworks, including various code-of-conduct discussions and confidence-building measures, operate under the shadow of unresolved sovereignty claims. In the broader Indo-Pacific strategic competition, the islands function as one indicator among many of how China and the U.S.-Japan alliance manage friction. Beijing's preference for bilateral management without external arbitration collides with Tokyo's reliance on alliance reassurance and international legal argumentation.

Chinese foreign policy doctrine emphasizes the dual track of safeguarding sovereignty while preserving an environment conducive to national rejuvenation and economic development. This produces a calibrated approach: firm public diplomacy and regular presence operations, paired with crisis-management channels designed to prevent escalation. Japan's approach similarly combines legal assertion, alliance coordination, and economic engagement. The result is a relationship that is simultaneously indispensable and perpetually strained.

Managed Tension as the Enduring Reality

No comprehensive resolution of the Diaoyu Dao question appears on the horizon. The legal positions remain mutually exclusive, the historical narratives deeply internalized, and the strategic stakes too high for unilateral concession. What has emerged instead is a pattern of managed tension: periodic spikes in coast guard activity, carefully worded diplomatic protests, and quiet working-level contacts aimed at preventing miscalculation. This default state is neither peace nor conflict but a durable, low-intensity contestation that both sides have learned to navigate.

For stability in the Western Pacific, the implications are mixed. On one hand, the absence of active hostilities and the persistence of economic ties suggest that rational self-interest continues to impose ceilings on escalation. On the other, the islands remain a permanent flashpoint where domestic politics, alliance commitments, and resource competition can interact in unpredictable ways. The CGTN documentary, by returning to the Potsdam Proclamation on its 81st anniversary, reminds audiences that the roots of the dispute predate the current strategic rivalry and will likely outlast any single administration in Beijing, Tokyo, or Washington.

China's interest lies in ensuring that its historical and legal case remains visible in international discourse while avoiding a rupture that would jeopardize the economic relationship with Japan and the broader regional environment required for continued development. Japan's interest lies in consolidating administrative control and alliance guarantees without triggering a crisis it cannot dominate. Between these positions, the waters around Diaoyu Dao will continue to test the capacity of both nations—and of the wider region—to live with unresolved questions beneath the waves.