In March 2004, the last time controversy over the Senkaku (Diaoyutai) islands surfaced, the US State Department affirmed that the United States Mutual Security Treaty with Japan covered the islands.

"The Senkaku Islands have been under the administrative control of the government of Japan since having been returned as part of the reversion of Okinawa in 1972," State Department spokesman Adam Ereli said. "Article 5 of the 1960 US-Japan Treaty of Mutual Cooperation and Security," he said, "states that the treaty applies to the territories under the administration of Japan; thus, Article 5 of the Mutual Security Treaty applies to the Senkaku islands."

So while the US may not take a position on "the ultimate sovereignty" of the islands, certainly their inclusion in the US security commitment to Japan makes apparent where its sympathies lie.

Where does sovereignty lie?

On the issue of sovereignty, let me make clear what the State Department cannot: The Senkaku islands are Japanese.

The Senkakus are a set of eight small uninhabited high islands in the rich fishing waters of the East China Sea that are administratively part of the Ryukyu island chain. They are defined under Article 3 of the San Francisco Peace Treaty as within the "Nansei Shoto" and the US was granted the "right to exercise all and any powers of administration, legislation and jurisdiction over the territory and inhabitants of these islands, including their territorial waters" by the treaty. The US occupied and administered them for 27 years after World War II and in 1972 returned the islands to Japanese sovereignty as part of the Okinawa Reversion.

Japan first claimed the Senkakus in January 1895 after decades of shipwrecks and near disasters had convinced Tokyo that lighthouses needed to be erected there. The claim on the Senkakus, as such, had nothing to do with Japan's colonial occupation of Taiwan as part of the settlement of the Sino-Japanese War that same year.

At the turn of the last century, President Ma Ying-jeou said, a Japanese businessman named Koga found that the main Senkaku Island held a fresh-water spring that could sustain about 200 people. He then brought workers, food and supplies to the main Senkaku Islands and built houses, reservoirs, docks, warehouses, sewers and farms for tuna fishing and canning. The tuna cannery business continued until World War II.

Clearly, for the purposes of international law, the Senkaku chain qualifies as "islands" because they are capable of "sustaining human habitation."

This is important because under the UN Convention on the Law of the Sea --to which both China and Japan are parties --an "island" brings to its owner a 200 nautical mile (370km) "exclusive economic zone" and sovereign claim to the resources and seabed minerals therein.

On May 15, 1972, after 25 years of military occupation, the US relinquished to Japan "all rights and interests" over the Okinawa territories, the State Department said, "including the Senkaku Islands, which we had been administering under Article of the Treaty."

Prior to 1969, neither Beijing nor Taipei indicated any desire for the Senkaku Islands. Maps printed in Taiwan before 1969 either failed to depict them entirely, failed to name them or included boundary delineations to the west of the islands (inferring they were in Japanese waters).

In my collection of maps, I have a facsimile of plate 18 of the Zhonghua Renmin Gongheguo Fen Sheng Ditu (People's Republic of China Provincial Map) of "Fujian Province, Taiwan Province" published in mimi (confidential) form by the Zhonghua Renmin Gongheguo Guojia Cehui Zongju (Headquarters, National Surveillance Bureau), Beijing, 1969, which identified the Senkaku Islands as the "Jiange Qundao" --using the Chinese characters for the Japanese name "Senkaku Island Group" --rather than the Chinese name "Diaoyu."

A People's Daily commentary of June 1953, which called on the people of Okinawa to resist the US imperialists occupying their homelands, enumerated the "Jiange" (Senkaku) islands as part of the Ryukyu chain, clear evidence that the Beijing government considered the islands part of Japan even in the heat of the Korean War.

Prior to 1968, no one in either Taipei or Beijing knew of any particular benefit in owning the Senkaku Islands. In 1968, however, geologists K.O. Emery and Hiroshi Niino, writing for the UN Economic Commission for Asia and the Far East (UNECAFE), noted that "a high probability exists that the continental shelf between Taiwan and Japan may be one of the most prolific oil reservoirs in the world."

While this news was greeted with some gratification in Japan, the Republic of China (Taiwan) government --then representing the Chinese mainland at the UN --was spurred into examining Chinese claims to the Senkaku Islands and the seabed oilfields within their orbit.

At one point, Chinese exiles in Taiwan claimed to have "deeds" to the islands granted to a Chinese courtier (and early patron of Chinese universities) Sheng Xuanhuai by the Qing Dynasty's Empress Cixi. This evidence gained currency in both Taiwan and Beijing and was proffered as the basis of China's historic ownership of the islands. However, recent scholarly consideration of this evidence tends toward the view that it is fraudulent. The documents of "deed" were not in the style of the Qing Dynasty, nor were the seals correct, nor was the paper of the quality used in Qing records.

Still, today, there are Chinese commentators in Taiwan who insist that the original deed to the Senkaku Islands was "kept in a bank safety deposit box" in Los Angeles, in the custody of Mme Chen Shien-chung, a "lineal granddaughter of Sheng Xuanhuai."

Although visions of Saudi-scale reservoirs in the East China Sea have now dissipated and the territorial waters issue is now mostly a matter of "face," oil and gas continue to be the currency of the dispute. Japan, believing that China's main interest was oil, long ago acquiesced in China's development of the "Chunxiao" gas beds ("Shirakaba" in Japanese), which lie astride the median line of the overlapping 200-mile exclusive economic zones (EEZ) of the two countries --if, and only if, the Senkaku islands' EEZ is counted as Japanese. In private conversations with Japanese officials I have learned an ironic fact --that the Chinese seabed pipeline from the gas field to the Chinese coast was partially financed by Japanese Overseas Development Assistance.

In an effort to assuage strained ties with China, and especially to ease frictions with Beijing over territorial waters, Japan has tried to get the Chinese to accept some "joint development" of the gas fields that straddle their respective EEZs --in return for China's acknowledgment of Japan's legitimate claims. But China has consistently rebuffed Japanese efforts to acknowledge that "joint development" of the Shirakaba field is predicated on a Japanese territorial sea claim.

Again, on June 18 the Chinese foreign ministry spokesman insisted that "China's consistent position and stance on the East China Sea issue have remained unchanged, Chunxiao oil and gas field falls completely within China's sovereignty rights and has nothing to do with joint development. When it comes to the East China Sea demarcation, China's position has stayed unchanged that it does not recognize the so-called 'median line.'"

By reaching out to Beijing and assisting China's development of the Shirakaba (Chunxiao) field without first getting some Chinese acknowledgment of Japan's territorial waters claim, Tokyo has made a tactical blunder. China is now in a position to pump dry the Shirakaba field and forestall Japanese action by dragging its heels on the demarcation issue. There are, however, at least three other fields that straddle the median line --Asunaro (Longjing), Kusunoki (Duanqiao) and Kashi (Tianwaitan) --but their delimitations are not dependent on the Senkaku Islands' EEZ boundary.

In 1972, Beijing's claims to the Senkaku Islands were delayed a bit by the Cultural Revolution and the Japan-China era of good feeling that persisted for a few years after the Beijing-Tokyo normalization of 1972. But by 2003 China's rivalry with Japan for the psychological leadership of Asia has impelled China to begin flexing its maritime muscle in the East China Sea.

By August 2005, Chinese fighter aircraft were shadowing Japanese P-3 surveillance aircraft in international waters close to the home islands.

For the first time, the Japanese press reported several years of previous incursions into Chinese waters and airspace by "suspicious" Chinese vessels. "Secret" documents from the Japan Self Defense Force reported that Chinese submarines had entered "in the area" of Japan's territorial waters at least six times in 2003. Chinese incursions into the Japanese EEZ became commonplace in 2004, with at least 12 EEZ violations by Chinese hydrographic vessels by May of that year.

In June, the Japanese media reported that Chinese submarines had entered Japanese territorial waters the previous November and had shown themselves "very comfortable" with marine characteristics of the Japanese coastline.

In October 2005, the fire-control radar aboard the Chinese Sovremennyy-class warship near the Shirakaba field had "locked-on" a Japanese P-3 patrol aircraft and there were reports that another Chinese naval vessel's artillery radar had targeted a Japanese coast guard vessel nearby.

Clearly, the Chinese were showing their teeth. By October 2006, Chinese military live-fire exercises in the East China Sea were rumored by the Hong Kong press to involve scenarios for an armed occupation of the Senkakus.

China's territorial aggressiveness in the East China Sea has alarmed Japan. Japan's national security bureaucracy clearly sees China as the primary challenge in Asia and is diverting large amounts of funding into missile defense, naval systems and new fighter aircraft.

But Beijing's diplomats are skilled --they have happily eased their pressures on Japan to woo it away from its concerns, and allies. And while Beijing now avoids antagonizing Tokyo directly, it certainly welcomes Taiwan's recent involvement in the Senkakus dispute. It helps China make the point that the issue is truly about "Chinese nationalism," not self-serving propaganda.

China's revered strategist of Confucian times, Sun Tzu, pointed out that while countering the enemy's strategy is of supreme importance, "next best is to divide him from his allies." The Senkakus issue threatens to alienate Taiwan from Japan. It also has the potential to strain Japan's trust in the US-Japan relationship. If the US views the recent flare-up as a minor spat between an immature Taiwan and a boorish Japan, and mutes its position, China may well begin to pressure Tokyo directly. Timidity on the part of the US could serve as a catalyst for a situation that goes against its Japanese ally, and ultimately its own interests, over the longer term.

Nothing good can come of a complacent Washington that allows Beijing to fill the leadership vacuum in Asia. The terms of the US-Japan Mutual Security Treaty are explicit regarding the Senkakus. It is time for Washington to face up to its responsibilities as an "ally" and make clear its sympathies on the Senkakus issue.

John Tkacik a senior research fellow at the Heritage Foundation in Washington, D.C., is a retired officer in the U.S. foreign service who served in Beijing, Guangzhou, Hong Kong and Taipei.