The sinking of the South Korean warship Cheonan, which occurred a year ago on March 26, has had a profound effect on relations between the U.S. and China, as well as between North and South Korea.

South Koreans raise the sunken ship, the Cheonan, in April 2010

The Cheonan sank when a torpedo exploded, killing 46 people. Few people doubt that the torpedo was launched by the North Koreans, but war between North and South Korea was avoided by a strange diplomatic dance by the South Koreans. (See “1-May-10 News — S. Korean and Chinese leaders meet to discuss warship sinking”)

North and South Korea were still technically at war, since the Korean war of the 1950s resulted in an armistice, not a peace agreement. North and South Korea had appeared to be moving toward some kind of peace agreement, and some people fantasized that the North and South could be reunited without bloodshed.

The sinking raised strong nationalistic feelings among the South Koreans, and many were demanding military retaliation. In order to avoid military action, South Korean President Lee Myung-bak artfully avoided accusing the North of being responsible for the explosion, for fear that merely saying so would also compel him to a declaration of war. He promised “resolute and unwavering” action over the warship sinking, once the international investigation has been completed, but then extended the investigation for many weeks. By the time the investigation was completed, tempers had cooled.

The investigation found that the torpedo exploded beneath the warship, causing a “shockwave and bubble effect” that fractured and split the ship. As part of the investigation, South Koreans trawled the sea floor beneath the site of the explosion and were able to recover torpedo parts that could be unambiguously identified as North Korea. (See “21-May-10 News — S. Korea accuses N. Korea of sinking warship”)

Finally the South Koreans had no choice but to accuse the Norks of sinking the Cheonan. This infuriated the Norks, who threatened war — which they do on a regular basis anyway. The Chinese refused to endorse the findings of the international investigation.

The South Koreans have adopted a number of “retaliatory” measures, short of military reprisals. They’ve conducted navy military drills off the coast, near the North Korean line, including joint exercises with American aircraft carriers. They’ve conducted a propaganda campaign, sending balloons with propaganda messages across the border into the North. Each of these acts brings as a response a hysterical threat of war from the North.

In November, the North Koreans shelled Yeonpyeong Island, a South Korean island near North Korea’s maritime border. The attack killed several South Korean civilians, and almost did result in war. (See “24-Nov-10 News — South Korean civilians shelled by North Koreans.”)

China refused to condemn the North Koreans. The Chinese proposed a resumption of the 6-way talks, but that proposal was rejected by the the U.S. and South Korea, since it would appear to be rewarding North Korea for their attack. The South Koreans became increasingly frustrated with the Chinese, who seem more interested in diverting attention away from the North Korean actions. The South Koreans are particularly angry at the Chinese for apparently sabotaging a United Nations investigation of the Yeonpyeong Island attack.

These events have significantly worsened US-Chinese relations, although Secretary of State Hillary Clinton was able to convince the Chinese recently not to veto the resolution authorizing military intervention in Libya — a decision which the Chinese now probably regret.

All of this comes at a time when much of North Korea is close to starvation, according to a report by the World Food Program (PDF).

According to the report, North has suffered a series of agricultural shocks in recent months, including very heavy rains in September and October of last year, reducing the rice and maize crops, and much colder than normal temperaturs in December and January, resulting in an expected 25% reduction in winter wheat yields.

The Public Distribution System will run out of food in May, and more than six million people will be in urgent need of international food assistance.

South Korea has provided food to the North in the past, but last year refused any further food aid until the North apologizes for the Cheonan and Yeonpyeong Island attacks.

Because of the severity of the food situation in the North, the South Koreans have announced that they will resume humanitarian aid for North Korean children only — powdered milk, nutritional cookies, and medical supplies — according to Chosun.

It’s now been four months since the attack on Yeonpyeong Island. If we’re to judge from history, it’s almost time for a new North Korean provocation of some kind.

I’ve felt for a long time that the North Koreans believe that they have nothing to lose by a war with the South. They know that the 1950s Korean War ended in an armistice, and they know that they’ve paid no price for subsequent provocations. I have little doubt that in some file cabinet in Pyongyang there’s plan that says they can capture Seoul overnight by sending a few hundred thousand N. Korean troops south across the border. They may even believe that once they’ve done that, the Americans will simply leave and let the Koreans work things out by themselves — with the North Koreans running the show.