When Lee Myung-bak, South Korea's president, reacted to the March 26 sinking of a South Korean warship with the loss of 46 lives by calling for an independent inquiry, the initial reaction was that he was playing for time. He probably was. To rush to the conclusion that North Korea had torpedoed the ship would have put him under pressure to retaliate, risking a dangerous military escalation with his unpredictable, nuclear-armed Stalinist neighbour. Now an international inquiry has confirmed that Pyongyang was responsible, the world has the option to take more measured, co-ordinated action. But to mount a credible international response, China – Pyongyang's most important ally – needs to be on boar