Almost a year ago, China and the Philippines were at loggerheads over their conflicting claims to ownership of the Scarborough Shoal fishing grounds and anchorage in the South China Sea, setting alarm bells ringing about a possible grab for control by Beijing in the maritime heart of Southeast Asia.

Today, the dispute still simmers, but the main zone of contention between China and its neighbors has moved to the East China Sea, where Beijing is contesting Tokyo’s sovereignty and administration over the Senkaku islands.

The confrontation between China and Japan, a key ally of the United States, has become one of East Asia’s most dangerous flash points. China says it was provoked to take strong retaliatory action after the Japanese government of Prime Minister Yoshihiko Noda bought three of the five uninhabited islands in the contested group from their private Japanese owner in September.

Japan had rented the three islands but banned landings or development on them to avoid antagonizing Beijing. But this arrangement was threatened by moves led by Shintaro Ishihara, the ultranationalist Tokyo governor at the time, to buy the islands and build fishing and other facilities there.

The intensifying struggle between Asia’s two top economies for control of the islands helped bring a conservative government under Prime Minister Shinzo Abe to power in December elections on a platform to strengthen Japan’s economy and defenses.

Since the “nationalization” of the islands, China has sought to portray Japan, despite its pacificism since 1945, as a threat to the region and a country intent on reviving its militarist past when it invaded much of Asia before and during World War II.

Yet the areas Beijing claims in the South China Sea are certainly far more valuable in the fisheries, energy and mineral resources they contain than the parts of the East China Sea contested with Japan.

Beijing’s claims in the South China Sea are also much more extensive than its claims in the East China Sea. The island and maritime zone disputed between China and Japan amounts to around 68,000 sq. km.

However, Beijing asserts sovereignty and other forms of jurisdiction over approximately 3 million sq. km, or about 80 percent, of the semi-enclosed South China Sea. This is nearly the size of India’s land territory (3.3 million sq. km).

The potential commercial and strategic value of the South China Sea is many times greater for Beijing than its relatively small claim against Japan in the East China Sea.

Why, then, has China been pursuing its claims against Japan over the disputed East China Sea islands in a much more muscular way in late 2012 and early 2013 than its case involving Southeast Asian claimants in the South China Sea?

It is evidently testing Japan and the U.S. at a time when each appears relatively weak and hesitant. Beijing knows that if it can make headway with its East China Sea island claim against two big allied powers like the U.S. and Japan, it will be easier in future to overawe its smaller Southeast Asian rival claimants in the South China Sea.

But Beijing also decided to intensify para-military and other operations against Japan, a nation whose wartime aggression is seared into Asian historical memory, because confrontations with smaller neighbors in the past few years have led to a regional backlash against China.

The result has been a rising mistrust of China, increased defense spending to guard against Chinese assertiveness, a turn to the U.S. as a counterbalance to Chinese power, the strengthening of U.S. alliances in Asia and development of security partnerships as a hedge against Chinese coercion.

Beijing faces an awkward propaganda problem in the South China Sea. Its claims are not against an original imperial or colonial power, as with Japan in the East China Sea.

Vietnam, the Philippines and Malaysia are Southeast Asia’s chief claimants to land features (islands, atolls and reefs) in the South China Sea. Tiny Brunei has a minor claim. Indonesia’s Exclusive Economic Zone — extending northwards from Natuna, the main Indonesian island territory in the South China Sea — overlaps in a substantial way with China’s far-flung claims.

Beijing’s claims in the South China Sea are against states that either fought or campaigned peacefully against colonial powers. In the case of Malaysia and Brunei, the colonial power was Britain. For the Philippines, it was the U.S. For Vietnam it is was France. For Indonesia, it was the Netherlands.

All these Southeast Asian countries have been proudly independent for decades. Many of them have demonstrated the same kind of stellar economic growth and competent government as China in recent years.

Like China, they have taken their place in the ranks of progressive developing and industrializing nations. They are universally acknowledged to be postcolonial successor states, as well as success stories.

These Southeast Asian nations with maritime claims in the South China Sea that overlap with those of China place a high premium on sovereignty and national rights, just as China does.

However, all the Southeast Asian countries involved are far smaller in population size, economic strength and military power than China. By these measures, Vietnam, the Philippines, Malaysia and Brunei are dwarfed by China, the world’s most populous nation and second-biggest economy and military spender. Even Indonesia, the fourth most-populous nation and Southeast Asia’s largest economy, is heavily outweighed by China.

China is therefore in an exposed propaganda position in the South China Sea. It can easily be portrayed as a regional bully. Indeed, it is cast in an aggressive light in countless news media reports, and government and nongovernment analyses, that circulate widely outside China.

The reputational damage to China’s international image and its self-proclaimed “peaceful rise” doctrine is already serious. It will get worse for as long as Beijing maintains what appears to most of the outside world to be a policy of overweening power and sabre-rattling.

Michael Richardson is a visiting senior research fellow at the Institute of South East Asian Studies in Singapore.