Iwakuni, near Hiroshima, is one of several military bases shared by American and Japanese forces. But behind the perimeter fence, US marines and Japan's Maritime Self Defence Force (a navy by any other name) live separately. To enter Japanese offices, US soldiers must untie their boots before stepping on the tatami.

The US-Japan Alliance, under which Washington is pledged to defend Tokyo in return for the right to station troops in the archipelago, has been the bedrock of Japan's peace and prosperity since the war. It has allowed Japan, until the 1990s at least, to go about the business of wealth-creation, safe under the US nuclear umbrella. But it has never been quite what it seemed.