Beijing has long been working to assert its sovereignty over the seas it shares with its neighbors. Its newly-declared air defense zone over the East China Sea is the latest tactic. And China has been working on another front — underwater. Its tool is archaeology.

China has a spectacular, but largely unknown maritime history. Beijing wants to make that history better known to the world and give substance to that narrative with archaeological evidence. For example, it would like to prove that islands disputed with Japan (known as Senkaku in Japan, and as Diaoyu in China) were first occupied by the Chinese and used as a base to combat Japanese pirates in the 16th century.

By digging up artificacts, China hopes to establish a historic claim of sovereignty over the islands, which would also give it a claim to the natural resources that may exist in and under the surrounding waters.

China has had a schizophrenic relationship with the sea. During 3000 years of history, China has had episodes of total isolationism, turning its back on the sea and literally removing all its citizens from within 10-20 miles of the sea, on pain of death. It has also had briefer episodes of widespread engagement, exploration and trade. Some people now talk about the 'maritime silk road.'

More commonly, China's maritime history has been something in-between. Most recently — and recent in Chinese terms is the last 200 years — the sea has represented humiliation. The 19th century witnessed repeated Chinese defeats at the hands of foreigners trying to gain influence and power over China's trade. In naval terms, this culminated in the trauma of the Sino-Japanese war of 1895, largely forgotten or unknown outside of Asia, which ended with the destruction of the Chinese Navy at the hands of the Japanese.

Since the late 1980s, China has been been in one of those episodes of heavy engagement with the outside world, seen most vividly in the spectacular growth of its international trade.

In terms of history, though, Beijing is emphasising what was the golden age of China's seapower. This was the early part of the Ming dynasty, or the 1400s in the Western calendar. It was an age personified by the admiral Zheng He, who led seven enormous expeditions, each lasting several years, around the littoral of the western Pacific and the Indian Ocean. His fleets reached as far as Kenya and Somalia, bringing giraffes and other tribute back to Beijing.

To back up this history, China is making a massive investment in underwater archaeology. And it is using its navy to kick foreign salvage crews out of disputed waters. Jeffrey Adams, an independent expert in international archaeological heritage management, says these efforts are signs that China is politicizing its maritime history.

"First, by celebrating their maritime golden age, and their great admiral Zheng," he says, "they reflect and reinforce the sense of nationalism for a domestic audience." For a foreign audience, he says, the Chinese can "peddle the image of Zheng He as [an] iron fist in a velvet glove as part of their soft power efforts toward promoting themselves culturally for foreign audiences to both reassure them and signal China's intentions."

Adams says the government could get further leverage from its archaeology by providing the information and artifacts for tourism and exhibits, and by partnering with Chinese technological and industrial concerns in its work. Finally, he says, the Chinese are using it as a hard power tactic, providing evidence for its territorial claims, and "pretence for conducting surveillance operations and enforcement of their claims."