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Probably nothing could be more damaging to the economies and general tranquility of China and Japan—and the region—than hostilities between them. Yet, spurred by intense and persistent nationalism, the two nations have been drifting toward at least sporadic confrontation with a mindless determination that sometimes belies rational judgment. The immediate cause: rival claims to own eight rocky isles, largely ignored for centuries but now thought to be surrounded by extensive oil and gas reserves deep beneath the sea.