

Shinzo Abe, now Japan's prime minister, on the campaign trail in December. (Buddhika Weerasinghe/Getty Images)

Before we get to the story of how Japan and South Korea came to be feuding over a bit of ammo-sharing between their peacekeeping forces in South Sudan, a bit of background to help you understand why this is all so absurd.

South Korea and Japan are arguably two of the most successful countries of the past half-century. They came out of their respective wars deeply impoverished and politically broken, but have since become wealthy and highly entrepreneurial democracies, renowned for their cultural exports and leadership in technological development.

It would make a lot of sense for South Korea and Japan to work closely together. They have similar economies, lots of cultural overlap, defense treaties with the United States, shared concerns about North Korea and a mutual desire to resist China's growing power and influence. The two countries stand to gain significantly from working together. But they are terrible at cooperating with one another -- just terrible.

Part of that has to do with rising nationalism in both countries, which can make cooperation with any foreign country difficult. But it has to do mainly with their shared history: Japan brutally colonized Korea in the first half of the 20th century, and then spent the second half becoming decreasingly apologetic, with senior Japanese politicians now treating that dark history as a source of national pride. South Korean politicians are not blameless themselves, playing up disputes and taking the bait at every provocation.

That brings us to the latest Korean-Japanese spat, which is both unsurprisingly petty and perhaps a new low. Both countries have about 300 troops deployed as peacekeepers in South Sudan, where internal conflict looks increasingly like the makings of a possible civil war. The South Korean troops needed more ammunition, which on Monday was supplied by the nearby Japanese force.

But what should have been a rare opportunity for cooperation has quickly become the opposite. South Korea said it asked the United Nations for ammo, and the United Nations just happened to pass along Japanese-owned bullets. Japan put out the story that the Koreans had asked them directly for the ammo. South Korea took this as an insult, apparently believing that Tokyo was attempting to spin the story to make Japan look strong and South Korea look weak. It has devolved rapidly from there, with national media in both countries playing up the grievances and offense-taking.

Seoul-based journalist Robert Koehler has the full, sordid story, complete with hyperventilating Korean media coverage. Here's where the dispute stands now:

The Korean side is now accusing the Japanese of politically using the emergency faced by Korean troops in South Sudan, with one unnamed official telling the Chosun Ilbo that the Abe government’s linking of the ammo supply to its “active pacifism” initiative was a “clear political provocation.” Another unnamed official said Korea had told the Japanese to handle this quietly out of fear that the locals would turn hostile and attack Korean troops if word got out that they’d received ammo, but the Japanese were instead turning this into a big story. Korean government officials are also saying that they intend to return all the ammo to Japan once Korean ammo arrives from Korea, despite the fact that the Japanese said they could keep it. The Japanese side, meanwhile, is pissed off with the Koreans — and not without reason, IMHO — for not only being ungrateful, but brazenly so. The Hani says one exasperated high-ranking Japanese government official was crying, “How the heck can we hold a summit with a nation like Korea?” It also seems that a lot of the alleged “noise” Japan was making was not to show off what they were doing for the Koreans, but rather to fend off domestic criticism that Abe and Co. were using the crisis in South Sudan to break Japan’s long-standing self-imposed ban on weapon exports.

The fact that this is all going down in the middle of South Sudan, a country with real problems, drives home how petty these spats are. Yes, South Korea and Japan have some very serious and real historical disputes that still matter today; some of the Korean "comfort women" used as sex slaves by the occupying Japanese forces in the 1940s are still alive and still occasionally insulted by Japanese politicians.

But neither country has much to gain, and both have a lot to lose, by holding on to those disputes rather than finding a way to cooperate. The fact that even a bit of conflict-zone ammo-sharing becomes a point of diplomatic dispute is a sign of just how tough it is for Korea and Japan to put their differences aside -- and a reminder of why China and the United States will continue to be East Asia's major players for a long time to come.