The US and Japan have quietly cornered the Chinese navy with an undersea surveillance ring that is framing Australia’s defence policy. By Hamish McDonald.

Japan and US enclose Chinese coast within sensor net

It’s about “humanitarian civil aid”, Australia’s Defence Department would have us believe. And, indeed, about 70 army engineers will duly be sent to work on projects in Philippine villages on Luzon and Palawan when Australia joins the militaries of the United States and the Philippines on Monday for 10 days of exercises.

Practising for “natural disasters” has become something of a cover story, it seems, for what is going on in the tightening network of American alliances in the Western Pacific since Barack Obama announced the annual rotation of a US Marine Corps taskforce through Darwin in November 2011 as a part of a strategic “pivot” or “rebalancing” to Asia.

But if it were just about cleaning up after cyclones, it is unlikely Canberra would be sending along one of the Royal Australian Air Force’s AP-3C Orions to Exercise Balikatan, as well as the engineers. Bristling with electronic, infra-red and magnetic sensors, acoustic buoys to drop, and onboard computing power, the aircraft is currently one of the world’s most advanced aerial platforms for detecting hostile ships and submarines and vacuuming up local communications.

In fact, the sea and air elements of Balikatan play out close to where Chinese dredgers have been frantically pumping sand onto coral reefs, also claimed by the Philippines and other South-East Asian states. The Filipinos themselves say the exercise will “increase our capability to defend our country from external aggression”.

The exercise comes just after the Centre for Strategic and International Studies, a Washington institution close to the thinking in the Pentagon, published before-and-after satellite pictures of the Chinese reclamation work in the Spratly Islands, and the visiting chief of the US Navy’s Pacific fleet, Admiral Harry Harris, told a Canberra audience about the “Great Wall of Sand” China was building far out from its coast, studded with ports and airstrips to intensify control over the South China Sea.

Meanwhile, Chinese ships and aircraft continue regular incursions around the Japanese-controlled Senkaku islands to the north-east of Taiwan, to assert claims of historical ownership. As recently as last year, Chinese fighter jets have jostled American patrol planes in the area.

With all this Chinese aggression, or “assertiveness” as it’s often more diplomatically put, you might be forgiven for thinking that the naval and air wings of the People’s Liberation Army have the Americans and Japanese on the backfoot, unwilling to risk a clash that the Chinese seem all too ready to escalate.

1 . 'Fish Hook' line

But a new study by two Australian experts suggests it is the Chinese who are cornered. Desmond Ball, the Australian National University nuclear strategist and analyst of electronic spy craft, and Richard Tanter, of Melbourne University, an expert on North-East Asian security and nuclear issues, suggest Japan and the US have China’s forces surrounded by trip-wires.

Their book, The Tools of Owatatsumi, reported here for the first time, details the networks of undersea hydrophones and magnetic anomaly detectors that, combined with data collected by ground stations, patrol aircraft and satellites, make it virtually impossible for Chinese ships and submarines to break out into the wider ocean undetected. In effect, a line of sensors has been drawn in the sea.

The trip-wire around the Chinese navy extends across the Tsushima Strait between Japan and Korea, and from Japan’s southern main island of Kyushu down past Taiwan to the Philippines. When first revealed, in a little-noticed article by Taiwan military intelligence official Liao Wen-chung in 2005, it was described as a “Fish Hook Undersea Defence Line”.

Controversially, the curve of the hook stretches across the Java Sea from Kalimantan to Java, across the Sunda Strait between Java and Sumatra, and from the northern tip of Sumatra along the eastern side of India’s Andaman and Nicobar island chain. Unlike the northern stretches around Japan and Taiwan, these extensions into South-East Asia would be largely American installed and operated.

Indonesia and India, both historic adherents of non-alignment despite recent warming to the US in the face of rising Chinese power, would be loath to admit to allowing the Americans to wire up their nearby waters, and would be perhaps even more embarrassed to learn that it had been done without their permission or knowledge.

Ball himself is not sure whether these South-East Asian sections of the line consist of fixed acoustic surveillance arrays in the manner of the long northern sections from Tsushima down past the Philippines. “I would expect the more southern segments to have been fully surveyed and prepared for expeditious deployment of other elements of the integrated undersea surveillance system in contingent circumstances,” he told The Saturday Paper.

These include towed arrays trailing behind surface ships and small acoustic sensors that can be scattered across the seabed unobtrusively at short notice in a program called the Advanced Deployable System.

“Outward movement of the Chinese subs based at Hainan would be very closely monitored, whether they headed south or north,” Ball said.

Information sharing between the US and Japan joins the undersea defence line up, effectively drawing a tight arc around South-East Asia, from the Bay of Bengal to Japan. Chinese vessels, above or below water, can’t move in or out of this net without being spotted by their rivals.

It is with all this in mind that one might reconsider the purpose of the US-led Exercise Balikatan in the Philippines – and the presence of the RAAF’s AP-3C Orion. It is for fishing inside the net.

The undersea system has not gone unnoticed by the Chinese. Their surveillance ships have sailed close to the Japanese shore stations where data from the arrays is processed. In 2006, Japan arrested for espionage a naval petty officer at its Tsushima Island anti-submarine base. He had made eight trips to Shanghai and been compromised by a relationship with a hostess from a karaoke bar.

In July 2013, Chinese newspapers reported that Japan and the US had built “very large underwater monitoring systems” north and south of Taiwan, and that large numbers of hydrophones had been installed “in Chinese waters” close to Chinese submarine bases.

More recently China has raised the alarm at the commissioning of Japan’s largest post-1945 warship, the helicopter carrier Izumo, which could be modified to carry the jump-jet version of the F-35 strike fighter, and at the Abe government’s floating of the idea of extending Japan’s air and sea patrols into the South China Sea.

“The underwater approaches to Japan are now guarded by the most advanced submarine detection system in the world,” Ball and Tanter write. In addition, the “Fish Hook” ensures that Chinese submarines are unable to move undetected from either the East China Sea or the South China Sea into the Pacific Ocean. “It suggests that even without recourse to the overwhelming US assets, Japan would be ascendant in any postulated submarine engagement with China,” they said.

While this leaves the Chinese able to reinforce their positions in the South China Sea against the weaker regional claimants to territory – Vietnam, Malaysia, Indonesia, Brunei, the Philippines and Taiwan as the alterative China – it might suggest a comfortable level of conventional deterrence held by Japan and reduce the prospect of war between East Asia’s two biggest powers and Australia’s two biggest trading partners.

2 . Risk of escalation

However, it raises two uncomfortable conclusions. One is that the US and Japan now have more reason than ever to discourage Taiwan from reunifying with the Chinese mainland, because it would irreparably break the trip-wire. Taiwan’s presidential election next January could see the Chinese nationalist party (Kuomintang) lose power to an opposition that has previously flirted with declaring independence. This would be another blow to China’s recent soft line of economic and people-to-people ties, encouraging Communist Party and PLA hardliners to think of sudden strikes.

The other, raised by Ball and Tanter, is the risk of uncontrolled escalation of clashes at sea or in the air. Japan’s superiority relies on these electronic surveillance facilities. While China might try jamming them, their isolated locations might tempt China into commando operations or strikes with guided weapons.

This vulnerability brings pressures to escalate any clash – on Japan to take out Chinese naval forces before the ability to track them is lost, on China to take out the shore stations first. Some facilities, such as the Japanese naval data processing centre at White Beach, Okinawa, “might be regarded as sufficiently important to warrant pre-emptive nuclear attack”, they write.

The US could not avoid entanglement. Aside from its treaty obligations to Japan, its own surveillance systems are co-located with Japan’s and the northern sections of the “Fish Hook” are as vital to US interests as those of Japan.

“The US Navy could not abide its degradation,” Ball and Tanter said. “At a minimum it would be compelled to attempt to destroy any Chinese missile-carrying submarines while aware of their locations, before they are able to pass through a broken ‘Fish Hook’ line and come within firing range of the continental United States.”

This is the standoff that our own defence forces are equipping themselves to join – with procurements of advanced submarines, air warfare destroyers, large amphibious ships, Poseidon and F-35 aircraft and drones – backed by “interoperability” with US and Japanese forces, and participation in exercises such as Balikatan.

At least we are starting to get a better idea of what type of engagements Australia should be preparing for, and what kind of conflicts might be regionally ignited.

This article was first published in the print edition of The Saturday Paper on April 18, 2015 as "Japan’s undersea spy battle with China".

For almost a decade, The Saturday Paper has published Australia’s leading writers and thinkers. We have pursued stories that are ignored elsewhere, covering them with sensitivity and depth. We have done this on refugee policy, on government integrity, on robo-debt, on aged care, on climate change, on the pandemic.

All our journalism is fiercely independent. It relies on the support of readers. By subscribing to The Saturday Paper, you are ensuring that we can continue to produce essential, issue-defining coverage, to dig out stories that take time, to doggedly hold to account politicians and the political class.

There are very few titles that have the freedom and the space to produce journalism like this. In a country with a concentration of media ownership unlike anything else in the world, it is vitally important. Your subscription helps make it possible.

Select your digital subscription

Month selector

Use your Google account to create your subscription