In recent weeks, Japan and China have squared off over who owns a minor group of islands in the East China Sea. The unthinkable -- a perilous maritime war for seemingly trivial stakes -- no longer appears unthinkable. So how do you defend a group of uninhabited rocks and islets like the Senkaku/Diaoyu islands?
Mainly by positioning yourself to win the air and sea battle around the disputed archipelago. The obvious way to ward off attack -- stationing garrisons and artillery on the tiny, resource-poor islands -- should be a secondary measure. And it would likely prove a losing one, absent superiority in nearby seas and skies. Forces left ashore without external support would find themselves stranded and outgunned, not to mention hungry and thirsty.
To be sure, heavily armed ground detachments can convert islands with rugged terrain into virtual "porcupines," prickly to the touch. For instance, Japan Ground Self-Defense Force (GSDF) troops equipped with truck-launched anti-ship cruise missiles could give any naval assault force fits. They could dig in, hardening their positions against air and missile bombardment. Despite their small numbers, GSDF defenders would be exceedingly tough to dislodge.
But only for a time. Whoever controls the sea and sky will ultimately determine the islands' fate. If U.S.-Japanese naval, air, and ground forces can hold open access to the islands while fending off Chinese assailants, the allies would stand to win a limited clash. They can resupply defenders perched there, letting them hold out more or less indefinitely. But if China's People's Liberation Army (PLA) wrests control of the air and sea commons from the allies, on the other hand, it will be at liberty to cordon off the islands and starve out the defenders. And then Beijing will stand to win.
Were a battle over the Senkakus/Diaoyus to take place today, I would give China the edge, even though Japan holds the contested real estate and the United States has committed itself to the islands' defense. Geography and force are the main reasons why.
First consider the islands' geographic merits and drawbacks. The great fin de siècle seapower theorist Alfred Thayer Mahan classifies geostrategic assets by their position, strength, and resources. The Senkakus/Diaoyus occupy an awkward position near the southern tip of the undefended Ryukyus chain, closer to Taiwan than to the Japanese main islands and roughly equidistant between Okinawa and the Chinese mainland. The archipelago's natural defenses are so-so at best, owing to its small size and fragmentation into several islets.
The island chain's geography opens up options for a determined attacker. Rather than mount a full-scale assault, PLA occupiers could grab one island, place weaponry on it, and pummel Japanese GSDF sites from there -- seizing the rest over time through salami-slicing tactics. And since the islets offer virtually no natural resources to support garrisons, everything would have to be shipped in by sea or air. If China rules even a pocket of sea and airspace around the islands, it will probably get its way in a test of arms.