North Korea's recent sinking of a South Korean warship was not an inexcusable act of aggression that came out of nowhere. It was an inexcusable act of aggression that had been building up for many years.
Though it was little noted in U.S. news reports, the maritime border between North Korea and South Korea—known as the Northern Limit Line—has been a frequent scene of naval clashes and confrontations over the last decade.
The March 26 incident, which killed 46 South Korean sailors and wounded many more, is by far the deadliest of these attacks and fully worthy of the condemnation it's received from the Obama administration, the U.N. secretary-general, and other world leaders.
But it is not unprecedented. In February 2002, an exchange of naval gunfire killed four South Korean sailors and wounded 18. A similar clash in June 1999 killed at least 17 sailors on a North Korean patrol boat.
According to a well-sourced chronology compiled by the military Web site GlobalSecurity.org, these were but two of at least 10 confrontations since 1999 in which North and South Korean vessels have fired weapons at each other along the Northern Limit Line.
All the incidents have followed a similar pattern. A North Korean patrol boat crosses the borderline; a South Korean vessel warns the boat by radio to back away, then fires a warning shot if there's no reply; at that point, either the two sides retreat or the confrontation escalates.
In most cases (as in the latest attack), North Korean officials deny that their boat crossed the line. Sometimes, they claim that the vessel was chasing illegal Chinese fishing boats (which, in some cases, may have been true). Once, though, after the incident of February 2002, Kim Jong-il's government initiated high-level diplomatic talks and sent North Korean athletes to compete in the Asian Games, which that year were hosted by South Korea. (These steps were interpreted as constituting an apology.) In the latest incident, the "Dear Leader"—as Kim is known in his national propaganda—reverted to form, threatening war if the United Nations so much as imposes sanctions.
Two of these naval skirmishes over the last decade—the first and the next-to-last—seem to have traumatized North Korean leaders the most. In June 1999, a North Korean boat crossed the line and fired the first shot. A South Korean vessel fired back, causing serious damage to the North's boat and killing at least 17 of its sailors. The North's political and military leaders, who had been publicly touting their great power for decades, were reportedly stunned by how swiftly they were defeated.
More recently, in November 2009, a North Korean patrol boat crossed the line. A South Korean vessel fired warning shots; the North fired back; the South then fired in earnest and again inflicted significant damage, setting the boat on fire (though no casualties were reported on either side).
Some speculate that Kim Jong-il may have planned the March 2010 attack as a show of strength, both to the Seoul government and to his own military commanders. South Korean president Lee Myung-bak had already—for good reasons—abandoned his predecessors' "sunshine policy" of outreach toward the North. Kim is also believed to be caught up in succession concerns—he is thought to be ailing and wants his youngest son, Jong Un, to be installed as his successor (just as he succeeded his own father, Kim Il-Sung)—and he may have felt a need to toughen up his image after the humiliation of last November.
You may notice the phrases believed to be, thought to be, and may have in the previous sentence. The fact is, Pyongyang is the most cloistered capital in the world (North Korea's widespread nickname is, after all, the "hermit kingdom"), and nobody on the outside—including U.S. and allied intelligence agencies—knows much of anything about its political machinations.
But this much is known: The Northern Limit Line, which Pyongyang's vessels have frequently crossed, is not exactly an artifact of international law. It was drawn in 1953 by the U.S. military forces that led the wartime United Nations Command; it wasn't officially recognized by North Korea; nor was it mentioned in the 1953 Armistice Agreement, which suspended the fighting. (The Korean War itself has never been declared over. The two countries are still, formally, in a state of war.)