This is fairly silly (describing a short-term effort to boost Japan's coast guard until new ships are built and crews trained):
Japan doesn't have a half-decade to wait around. So commanders have whipped up an emergency solution: They'll bring 10 ships out of mothballs -- all of which are a quarter-century old or more -- that would otherwise be turned into scrap metal. Even better, they're going to be crewed by old people.
Okay, that's unfair. We probably aren't talking about senior citizens manning the deck guns like Peter Berg made them do in Battleship; many of these "retirees" likely ended their service at a relatively young age. Even so, the case reveals some of Japan's long-term challenges. Put simply, we're talking about a fully developed country that's approaching the limits of its human resources. This is a problem for Japan that is neither new nor going away: over the next 50 years, its population is expected to contract by another 30 percent.
This is not something caused by the limits of manpower. I'm reasonably sure that it is simply quicker to pay retirees familiar with the ships than to train new people to operate ships that are interim vessels only.
Consider Japan's population (I'm using 2008 publication figures here). So Japan has 127,000,000 people. With 9% of the population being males from the age of 15-29, just to have a rough idea of manpower resources. Japan actually has 240,000 active duty personnel. Do you really think Japan recalled retirees because they don't have enough people to serve?
Let's compare Japan to America, then. Population: 301,000,000. 11% of our population is composed of males aged 15-29. We've got more military age males, but it isn't that dramatically different. And we support 1.5 million active duty personnel. So with about 2.4 times more people, we support a military more than 6 times larger than Japan's.
Japan is not short of people to man their military.
And the military power that matters in a Japan-China contest is air and naval power, the 2 areas most receptive to technological solutions to replace manpower.
So yes, Japan can take a leading regional defense role if they choose, despite their declining population. They have not reached the limits of their human resources. Unless you think that Japan and China might be involved in a protracted land war, looking for demographic limits to Japanese military power is nonsense.
I can't believe that article was published.
UPDATE: And remember, I think non-personnel solutions are there for ground forces to occupy and defend the Senkaku Islands.