Making predictions about world security is usually a mug's game, but here is one you can bank on for the vast Asia-Pacific region.

A North Korean sentry looks south from his side of the truce village of Panmunjom, a mere 55 kilometres from Seoul. (Jo Yong-Hak/Reuters)

It is that the monumental new arms build-up there by at least a half-dozen nations, in particular China, India and Japan, will soon alter the security realities that have existed under six decades of an all-powerful U.S. naval presence.

The region is already tense as a result of recent flare-ups on the Korean peninsula and angry disputes at sea between Japan and China.

But the issue here goes far deeper and has more to do with future capabilities than the current intentions of the different protagonists.

Right now, the capabilities of the rising powers, China and India, along with a relative weakening of U.S. military dominance in the region, ensures a multi-nation scramble to reshape sea power in the 21st century.

Open jostling

There is still a strong belief among global strategists that the 19th-century American naval historian Alfred Mahan was right when he asserted that the nation with the most powerful navy would control the globe. (If Mahan were around today, he would likely expand that axiom from nation to alliance.)

Last year alone, almost $6 trillion in trade was plied along the sea routes off South Korea, Japan, China and Vietnam, while half of all global trade passed through the Indian Ocean.

A crisis in either body of water would affect the entire world economy.

What 2010 gave us was some open jostling by the rising powers in this region to identify their "spheres of influence." But this jostling is merely a symptom of much larger tensions.

The Western Pacific, the American view from a vintage CIA map that includes the Japan and China seas down to the Bay of Bengal and the Indian Ocean. (CIA map)

Long a weak naval nation, China has clearly indicated that it is fed up with American efforts to "contain" Chinese authority in the Pacific.

Beijing is now expanding its maritime forces far offshore to try to force the big U.S. warships out of much of the Western Pacific.

India, meanwhile, nervous about China's long-term ambitions, increasingly frets about the growing presence of Chinese naval vessels and port facilities in the Indian Ocean, an area New Delhi feels belongs in its security zone.

As a result, India is now expanding its naval plans to include three new aircraft carriers and several nuclear-powered stealth submarines.

But most nervous of all is Japan, which has in its orbit both erratic North Korea and an expanding China to worry about.

Japan re-girds

An indication of Japan's anxiety is its remarkable new national defence plan, which was leaked in December by Japanese media.

The plan essentially reverses decades of passive Japanese planning to defend its northern islands against Russia and, instead, focuses on confronting threats from North Korea and especially China.

In coming years, Japan will deploy new submarines, destroyers and top-notch F-22 fighter planes to cover the sea approaches off its southern islands, including Okinawa, an area now the subject of a bitter Sino-Japanese diplomatic clash over sea rights.

Even more startling, Japan now seems ready to drop its usual quasi-isolationist stance in order to enter into close naval exercises with the U.S., South Korea, Australia and India.

A Japanese destroyer sails alongside the USS George Washington aircraft carrier during joint naval exercises in December 2010. (Reuters)

Some naval planners expect this will evolve into the core of a new maritime defence alliance.

China's might

As for China, it appears to seek nothing less than an historic shift in the Asia-Pacific balance of power.

Other nations are still unclear about the extent of China's maritime ambition. But many security experts are convinced it wants, at the very least, a dominant presence over the Yellow Sea, East China Sea and South China Sea — meaning areas up to 2,000 kilometres off its coast.

That's a vast reach and it covers the sea lanes of South Korea, Japan, Vietnam and even the Philippines. All would fall under what naval strategists call a potential anti-access/area denial zone.

But to project such power, China needs to restrain the mighty U.S. Pacific fleet and its carrier task forces from the kind of easy domination of the region that it has enjoyed since the Second World War. (At times, during the Cold War, U.S. ships were confident enough to sail within 12 nautical miles of China's coast.)

In building its naval might, China has been remarkably patient and steady.

Back in the early 1990s, it decided to avoid the kind of economically ruinous arms race with the U.S. that collapsed the Soviet Union.

Instead it concentrated on an intensely focused build-up of new nuclear-powered stealth submarines, surface ships and what the Pentagon has called "the most active land-based ballistic and cruise missile program in the world."

It is these missiles that now threaten to change the whole strategic balance.

Game changer

The greatest concern to Washington and its allies, is a Chinese weapon that may revolutionize sea power in this part of the globe — the world's first anti-ship ballistic missile, the Dong Feng 21D.

The missile is reportedly precise, carries a heavy warhead and is specifically designed as an "aircraft carrier killer."

With a range of 2,000 kilometres, the 21D has already reached operational capability, according to the Pentagon, and is expected to be fully deployed within two years.

The potential importance of this move cannot be overestimated.

America's Pacific control has depended overwhelming on carriers and their air power.

But carriers are giant floating cities with crews of 6,000. In times of crisis any U.S. admiral is going to be reluctant to risk such a behemoth inside that 2,000-kilometre "kill zone."

As things now stand, if the carriers hold back, U.S. Pacific power is considerably weakened.

Cycle of reward and resentment

The U.S. has no illusions here. Defence Secretary Robert Gates recently warned that these new anti-ship missiles "could threaten America's primary way to project power and help allies in the Pacific, in particular our forward aid bases and carrier strike groups."

A Chinese pilot in a Jian-10 fighter jet in April 2010. China at that point had the world's third largest air force with an estimated 400,000 personnel and some 2,000 combat aircraft. (Petar Kujundzic/Reuters)

As one response, Washington is reportedly doing more "out of sight" by deploying more of its 31 fast-attack submarines and three Ohio class submarines to the Pacific.

It's also working flat out to try and devise electronic countermeasures against the 21D missiles.

Meanwhile, diplomatic relations between China and the U.S. continue to blow hot and cold.

No one is talking about a Cold War-style showdown at sea, at least not yet. Strategists talk rather of the use of the naval threat in peacetime to gain area dominance, the age-old tactic of empires and trading blocs since the time of sail.

Both China and the U.S. need each other for trade. But today, trade is making China stronger and inevitably this leads to military strength, which the U.S. in turn fears and resents.

It is a constant cycle of reward and resentment, which may well be containable, as some Chinese writers have suggested. But when such tensions revolve around the richest trade routes in the world, other countries are inevitably brought into the struggle.

So far, Canada has stayed somewhat aloof from the Asia-Pacific arms build-up, but it will certainly come under renewed pressure from any new Western-oriented alliance to improve its military cooperation in the region.

As noted, when gauging future security, countries have to look to the capabilities of their rivals, not simply their stated intentions.

When it comes to China at sea, no one takes these capabilities lightly anymore.