Territorial disputes and China's air defense identification zone have focused new attention on the question.
Regional ties are at a new low since China's unilateral announcement, but China may be willing to endure short-term displeasure for long-term gains.
Beijing wants to change the status quo in the East China Sea. US officials think it unlikely that China will challenge military flights.
Two-and-a-half years after the disaster, the nuclear plant continues to pose problems. Here's what you need to know now.
More than two years after a massive earthquake and tsunami caused a nuclear disaster at Japan's Fukushima Daiichi nuclear power plant, the embattled operator is stuck in damage-control mode.
Fukushima nuclear power plant: Officials say they don't know how 10 workers at the plant were sprayed with radioactive water recently.
Nagasaki bombing: Sixty-eight years ago, the US dropped an atomic bomb on the Japanese city, just three days after the attack on Hiroshima.
China blasted Japan's 'white paper' defense report about its maritime activities as 'untruthful.'