Both South Korea and Japan have peacekeepers in South Sudan where, for the last two months, there has been a civil war. When the civil war began in mid-December the South Koreans found they didn’t have enough ammo for any sustained action, something they might now have to deal with given the number of locals shooting at each other and the civilians and foreign aid workers the South Korean troops would have to defend. So on December 22nd they asked the nearby Japanese contingent if they could spare any ammo and the Japanese promptly sent 10,000 rounds. It turned out that the additional ammo was not needed and on January 10th it was returned to the Japanese.
All this was a big deal in South Korea, where hatred of Japan has been a major national passion for over a century. Although South Korea and Japan have many reasons to be allies, they have a difficult time making formal agreements to cooperate against North Koreas or Chinese aggression. When pressed on this South Korea points out that because of the widespread antipathy towards Japan for past events the Japanese must do something dramatic to improve their popularity in South Korea. This quick loan of ammunition was not all that dramatic, but it does help.
The South Korea anger towards Japan can be traced back to when Korea was a brutally treated Japanese possession from 1910 to 1945. The four decades of Japanese occupation were very cruel. Think how bad the Nazi occupation of conquered countries was during World War II and realize that the Japanese occupation of Korea was much worse and for much longer. The Japanese don’t help with their post-World War II attitude that Japan was a victim because it was forced into World War II by evil Westerners and was only trying to help its neighbors by occupying them and treating them badly. Japanese have a hard time understanding how their victims don’t appreciate all that Japan tried to do for them. What the foreigners do remember is what the Japanese did to them, something the Japanese tend to downplay or deny outright.
It’s popular in Japan to believe that after they defeated, after a brief war, Russia in 1905 they should have been accorded more respect by the West. The Japanese seemed to overlook that fact that most European countries had defeated Russia a one time or another. Even Sweden had done so, and later on even tiny Finland would as well. The problem here was that everyone but Japan saw Japan as a major bad guy during World War II.
As a result of the 1904-5 Russo-Japanese War Japan got control over Korea in 1910, along with some German colonies a decade later for joining the allies during World War I. Japan expected more for its World War I support and these resentments led to increased aggression against China and, eventually, to attacking the United States and European possessions in East Asia in 1941. The United States liberated what is now South Korea while the Russians did the same in North Korea.
Officially, South Korea suggests that Japan cede to South Korea claims on Dokdo Island in order to improve relations. South Korea has long been willing to sacrifice good relations with Japan over the issue of who owns the uninhabited Dokdo (Takeshima to the Japanese) islands in the Sea of Japan (East Sea in Korean). Both countries have been sending more air naval reconnaissance missions to the islands, and the mass media in both countries have been jumping all over the tension. Japanese politicians would take an enormous domestic political hit if they managed to get the votes to give South Korea Dokdo. But it would make Japan popular enough in South Korea to get the long-desired (by defense officials in both countries) cooperation treaty.