[dsp1234]

Waste of effort, too?

As an air defense base, yes. As a FOB for non-wartime activities, no. As a defensible base in an all out war, yes.

That said, I can't imagine Diego Garcia's primary role is to act as a buffer/barrier so the two aren't really comparable in that way. After all, it has:

"two parallel 12,000-foot-long (3,700 m) runways, expansive parking aprons for heavy bombers, 20 new anchorages in the lagoon, a deep-water pier, port facilities for the largest naval vessels in the American or British fleet, aircraft hangars, maintenance buildings and an air terminal, a 1,340,000 barrels (213,000 m3) fuel storage area, and billeting and messing facilities for thousands of sailors and support personnel."

Is this comparable to what the is being done by the Chinese?

[Someone]

The comment I reacted to mentioned the strategy of the Japanese in World War Two. They had islands with lots of infrastructure (for the time), too.

I think the problem for the Japanese was that they didn't have enough ships. Knowing that, they went for the island approach. Doing that, they gave up mobility in exchange for size and robustness. The mobility of the US navy allowed the US to concentrate firepower and take an island at a time. If distances between islands were smaller the Japanese might have been able to better defend against the US by rapidly moving planes and infantry between islands.

[hga]

They also didn't have enough planes, the ability to make significantly better ones due to the engines, and not enough pilots (they didn't change to war tempo pilot instruction until way too late). They really had no business getting into a war with a mature and robust industrial power like us, their only hope was breaking our will and that, at best, would have only happened when we started invading the home islands.

The war was all but over after the South Pacific campaign which started with our landing in Guadalcanal. Neither of us did anything particularly clever there, besides our only neutralizing vs. taking Rabaul, it was just a brutal slugfest where, for example, in one night action we lost two rear admirals (2 stars). By the end of it, IJN airpower, land and carrier based, was broken, and most of that was done by US land based aviation. For a really in depth look this book is highly recommended: http://www.amazon.com/gp/product/0813338697

You do have a point about our tactic of defeat in detail, when we were willing to expend enough lives and material we could and did take islands as we needed. I guess one of their big mistakes was thinking they could stop that for any particularly island with their air and naval forces in the region.