While Chinese athletes try to gobble up Olympic gold in London, half a world away Chinese strategists are trying to gobble up vast tracts of contested territory in the South China Sea.

Without strong push back, Beijing may be able to do just that.

You see, Beijing believes many of these South China Sea islands (and their adjacent waters) are “indisputable” Chinese territory, despite their often great distances from China itself and proximity to other nations.

The problem is countries such as Vietnam, the Philippines, Brunei, Malaysia and Taiwan also claim territory in places with names like the Spratly and Paracel Islands.

Not surprisingly, these areas may have lots of natural resources; some estimate the seabed could hold more than 200 billion barrels of oil and nearly 900 trillion cubic feet of natural gas.

That’s huge.

Adding to China’s questionable historical and legal claims to these areas is a recent Beijing announcement that China is establishing a military garrison in the Paracels, which would look after Beijing’s “claims” in the South China Sea.

While previously the Chinese coast guards’ duty, it now appears Beijing will militarize the disputes within its so-called “nine-dash line” that outlines its claim to roughly 80 percent of the nearly 1.5-million square mile South China Sea.

What’s also interesting about this is that China increasingly has the naval forces to throw its weight around in East Asia after years of being anything but a maritime power.

For instance, it’s developing an aircraft carrier and an air wing to operate off it. It has new attack submarines and blue-water destroyers, plus a unique land-based ballistic missile that can take out carriers.

OK, but why should we care?

First the United States is a Pacific nation. Nearly half our global trade is with East Asia; additional trade passes through the region to places like South Asia and the Middle East.

With trillions of dollars in ship-borne trade sailing the South China Sea annually, freedom of the seas through this “global common” is important to U.S. interests.

We’ve also got lots of allies and old — and new — friends in the region that are unnerved by Chinese boldness and brutish behavior such as (defense treaty ally) Philippines and Vietnam.

Plus if Beijing’s assertiveness is ignored, or acquiesced to, who knows what might come next?

China already feels encouraged — and driven — by lust for natural resources and perceptions of regional players’ weaknesses.

Unfortunately, while the Pentagon claims its Asia strategic “pivot” will shift half the Navy’s ships to the Pacific, it might be tough to do, considering Middle East commitments and ship numbers falling below requirements by nearly 30 in the coming years.

The geopolitical storm clouds forming over the South China Sea provide only the latest in a series of reasons for ensuring we have a strong national defense, especially our Navy, to look after our national interests — even in tough economic times.

Peter Brookes is a Heritage Foundation senior fellow and a former deputy assistant secretary of defense.