Japanese Surveillance
A Japanese Self-Defense Force P-3C maritime surveillance plane passes by the Senkaku/Diaoyu islands. Reuters

Japan and China have a lot to gain from being friends: trade between the two in 2010 was valued at $300 billion. But that hasn't stopped the two countries from intensifying their mutual accusations amid heated maritime disputes.

In past years, Japanese defense white papers released by the country's Ministry of Defense have blasted China's military growth, calling it alarming and opaque. This year has been no different.

(The U.S., which has also been highly worried about Chinese military transparency, nevertheless shared a $500 billion trade relationship with China in 2011.)

China has regularly replied that Japan's remarks on its military spending are irresponsible and unduly jeopardizes any improvement in their relations.

This year, Tokyo's new report, released on Tuesday, added new warnings about China's stability and civil-military relations in a critical year of transition (late 2012 will see top echelons of the Chinese Communist Party decide on the country's future ruling oligarchy). The Japanese Defense Ministry noted that the Chinese military had a "changing" influence on the foreign policy community, and that it now had a "complicated" relationship vis-à-vis the party. "Factors that could destabilize the management of the government are expanding and diversifying (due to the spread of the Internet and other reasons)," said the report.

Some of the above appear at first glance to be vague terms for sure. Haven't party-military relations always been complex? China is a Communist state, after all. And can we really expect the Chinese military to have unchanging influence on foreign policy when it receives tens of billions of dollars more every year from the central government?

The rather unspecific language may instead be a hint at Japanese worries that the Chinese military is now exerting increasing influence in state decision-making, especially in matters related to key territorial disputes in the region. In other words, Tokyo suspects that the Chinese government is adopting a harsher line to deal with territorial disputes, championed by the military, rather than the more conciliatory tone which used to be carried by the Foreign Ministry.

Regardless of whether that were truly the case, some things can be deduced with greater certainty outside the realm of speculation.

China's defense spending, for example, has been undeniably large. The 2012 Japanese report claims that China's annual defense budget has more than doubled since 2007 and "has increased about 30-fold during the past 24 years."

Indeed, this year China is officially spending more than $100 billion on the military; in 2006, it was a little more than $35 billion.

East Asia watchers won't be particularly shocked to hear that the Japanese government has increased its verbal warnings about China's military growth. The country's ongoing dispute with China over ownership of the Senkaku / Diaoyu Islands has long been a thorn in the side of bilateral relations. Recent bickering -- over Tokyo's decision to "nationalize" the islands by purchasing them from a private owner -- has only demonstrated the staying power of the dispute, and its growing political value to leaders in both countries as a tool to shore up domestic support.

The Japanese report asks for the government to increase surveillance over the island group, and adds that China has been "expanding and intensifying its activities in waters close to Japan." Japanese media have highlighted Chinese fleets transiting into the Pacific from the East China Sea through the Okinawa Islands, which is largely seen in Japan as a violation of territorial waters. Attention is also being given to China's new aircraft carrier, which for a maritime-conscious nation like Japan may be particularly distressing.

Tokyo's defense white paper added that beyond Japan, China's military growth was also "a matter of concern for the region and the international community," likely alluding to recent tensions between China and South China Sea neighbors. The Japanese defense ministry criticized the Chinese government for being unwilling to disclose a more detailed breakdown of its military spending.

China hasn't been the only country irked by comments from Japan's new report. Both Koreas have disputes with Japan over the status of a group of islands they call Dokdo (South Korea administers the islands and stations a small garrison there), but Japan labels as Takeshima.

Japan's report has called the islands its "inherent territory," prompting Seoul to summon a deputy mission chief from the Japanese Embassy for a harsh talking-to on Tuesday. The South Korean Foreign Ministry said on the same day that the government would "not allow any kinds of territorial claims on Dokdo by Japan."

In early July, a security pact between South Korea and Japan which would have allowed closer intelligence sharing and cooperation fell apart at the last minute due to strong domestic resistance in Korea. The new agreement had long been supported by the U.S. as a means to bridge divisions between its Asian allies, and was previously -- and for now, erroneously -- heralded as an indicator of strengthening relations between Seoul and Tokyo due to common concerns about both North Korea and China.

On July 26, Japanese Prime Minister Yoshihiko Noda said that "In case a neighboring country engages in illegal acts on our territorial soil and in our territorial waters, including the Senkaku Islands, we will react resolutely, including the possible use of the Self-Defense Forces as the need arises."

The Chinese foreign ministry responded on July 27 by saying that "Nothing can shake China's resolve and determination to safeguard its territorial sovereignty. China has expressed its grave concerns and strong dissatisfaction with Japan's extremely irresponsible remarks ... Japan should earnestly uphold the larger interests of bilateral relations and make concrete efforts to properly handle relevant issues."

But it appears that both governments are deeply concerned that their battle of words would ultimately translate into humiliating and difficult to manage incidents at sea. On July 28, Japanese media reported that Beijing and Tokyo had already agreed to establish the foundations for creating a formal hotline between their leaders to alleviate tensions at sea.