Defense communications between China and Japan were interrupted and bilateral ties became tense after a Chinese trawler collided with Japan Coast Guard ships in September last year near Diaoyu Islands. Despite the untoward development, China responded sympathetically, both at the government and non-government levels, to the March 11 earthquake that devastated Japan, warming bilateral relations.

But Japan's white paper on defense, issued recently, has once again hurt bilateral relations by playing up the "China threat" theory.

The March earthquake and the ensuing tsunami and the Fukushima Daiichi nuclear power plant accident (or triple disaster) have not only hurt the Japanese economy, but also have had a deep impact on its strategic role in the region. Japan has territorial disputes with Russia, the Republic of Korea (ROK) and China, but all the three countries offered aid to it after the quake and tsunami. In spite of that, Tokyo has taken policy decisions under the influence of the US-Japan military alliance and according to its energy demand.

Japan's current foreign policy and the impact of the triple disaster on the Asia-Pacific region's economy and strategic situation will influence international relations in Asia Pacific in the long run.

The US returned to the region last year with its new Asia-Pacific strategy to build a "gooselike security pattern" to tackle China's rise. The US places itself as the leader of Asia Pacific, followed by the US-Japan and US-ROK alliances. The third tier of the US' security ring is its relationship with allies such as Australia, the Philippines and Thailand, and the fourth is its ties with Vietnam, Indonesia and India.

After Japan's triple disaster and Washington's return to the region, the US-led alliance has become more multilateral and expanded its network further. It means that China will face a more united and tighter US-led military alliance in its competition to take the leadership role in East Asian security in the short run.

Besides, the triple disaster will strengthen the asymmetrical US-Japan alliance. Protests and strong opposition in Okinawa, Japan, in 2010 had prevented the Japanese government from signing an agreement with the US on the Futenma Air Station relocation issue. But because of the prompt and large-scale relief provided by the US Forces in Japan (USFJ), Japanese people saw the positive side of US-Japan alliance.

The USFJ's relief work could to a certain extent mitigate Okinawa residents' repulsion against the American military base even though Okinawa prefecture suffered little from the triple disaster, but it cannot altogether quell local people's anger.

The triple disaster has laid bare the asymmetrical character of the US-Japan alliance. But Japanese people's opposition to it is likely to weaken as Tokyo's security dependence on Washington grows.

Since Japan's nuclear energy development plan will be delayed, it will rely more on import of oil and deepen its trust in the US to protect its interests in waterways as distant as the Persian Gulf. Many scholars believe that the huge impact of the triple disaster on Japanese people is likely to become the most important factor influencing their self-cognition and opinion toward the US-Japan alliance in the long run.

The triple disaster has played the role of an activator, examining and intensifying Japan's cooperation with the US. Japan's relationship with the ROK has improved, too, because of the triple disaster, giving a shot in the arm to the US-Japan-ROK coalition in Northeast Asia. Australia has also played a very active role in this development.

The overflowing impact of the triple disaster has highlighted the necessity and urgency of non-traditional security cooperation in Asia Pacific, especially among East Asian countries.

China, Japan and the ROK have strengthened communications and cooperation in warning against earthquakes and other natural disasters. According to Japanese Foreign Minister Takeaki Matsumoto, the Japanese government is preparing for "revival diplomacy" aimed at helping rebuild quake- and tsunami-hit areas.

Cooperation in non-traditional security is less sensitive than in traditional security because common interests are above competition and could help reduce doubts and build mutual trust among countries. But considering the dominant role that the US has played in relief and rescue operations in Japan and the strong constraints China's rescue team faced, we have to assess the US factor in its entirety while promoting non-traditional security cooperation in East Asia.

The triple disaster has improved Japan-Russia ties, even if temporarily. Japan's increasing demand for natural gas from Russia would force China to face more competition in acquiring energy resources. After the nuclear leak from the Fukushima Daiichi plant, Japan was forced to shut down or suspend many nuclear power plants. As a result, it has had to import more oil and natural gas. Statistics show that Japan's import of liquefied natural gas (LNG) in April 2011 increased by 23 percent year-on-year.

Japan's increasing demand for oil and LNG will make it more dependent on Russia. It is thus possible that competition between China and Japan for importing oil and gas will become fiercer, creating more challenges for Beijing to secure the supply of its energy resources.

The authors are with the Institute of Asia and Pacific Studies, China Academy of Social Sciences.