WHAT IS to be done when a rogue state commits an act of war, killing scores of people, but tries to avoid retaliation by denying responsibility? For South Korean President Lee Myung-bak, the answer begins with a very deliberate investigation. It has now been more than a month since the March 26 sinking of a South Korean corvette after an explosion; a week of mourning is now underway for the 40 sailors killed and the six still missing. From the beginning, an attack by North Korea was suspected. But only this week did South Korea's defense minister say publicly that a torpedo was the likely cause of the explosion -- and he didn't say where the torpedo came from.
Even that cautious statement was quickly played down by the Obama administration, which is participating in an international investigation of the incident. "I think it was a conditional statement," said State Department spokesman Philip Crowley. "I don't know that the investigation has arrived at that final judgment."
Investigators have yet to find hard evidence, such as scraps of a torpedo. But the real problem of concluding that North Korea did what it almost certainly did is that neither Mr. Lee nor the Obama administration has good ideas for how to respond. Military retaliation would risk a devastating war on the Korean Peninsula. Asking the U.N. Security Council for more sanctions against the regime of Kim Jong Il would require the consent of China, which will not easily be persuaded. And unilateral sanctions by South Korea, such as closing an industrial area where Southern firms employ thousands of Northern workers, could make the North still more dependent on China, which already controls 70 percent of its trade.
Mr. Lee has handled the situation as well as he probably could. He has avoided provocative public statements while trying to build a national consensus that excludes military action, and an international agreement that North Korea must suffer some consequences. Tighter sanctions might serve a purpose if they force Mr. Kim to resume negotiations about giving up his nuclear arsenal; they might also further weaken a regime that has been looking particularly shaky to some outside experts.
Still, North Korea is likely to survive so long as China continues to prop it up. Since Beijing appears to prefer the status quo on the Korean Peninsula, it is unlikely to withdraw its support anytime soon. That means, in turn, that Mr. Kim has a good chance at getting away with murder -- which is probably what he calculated all along.