My second attempt at blogging lasted for a few weeks in February-March 2003, and petered out after the Djindjic assassination. I only really got into my stride whe I set up this blog in May.
From the Heart of Europe
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I suppose the flip answer to your question is, “the same way as any other country with half Japan’s population”. In Fumigashi’s story (so far at least) women take on traditional male roles, including the military (though many of the surviving men are also warriors).
But I do wonder if defence in the way you put the question was really an issue for the secluded Japan of the mid-eighteenth century? Was Japan actually under external military threat before 1808? I don’t know the answers myself.
It’s also possible, I suppose, that in Fumigashi’s world, Japan’s geographical neighbours have also had their men die off, so everyone is in the same boat. The only foreigners we see are the Dutch. (Though I infer so far that the problem is one largely restricted to Fumigashi’s Japan.)