It may have been the worst kept secret in the region, but the official conclusion that it was a North Korean torpedo that sunk a South Korean warship in March brings fresh and potentially damaging complications for China.
In Seoul, South Korean officials insist they are now pushing Beijing for far greater involvement in pressuring Pyongyang, China's fraternal but prickly ally.
In coming days that is certain to mean pressure for China's acceptance of tough new sanctions via the UN Security Council and/or a swift apology from North Korea, a recalcitrant state hardly known for its mea culpas in the past.
And while China, together with the US, is likely to be cautioning South Korea against any action that provokes escalation from their North Korean enemies, Seoul has deliberately not taken a possible military response off the table.
'I'm sure China would like to swiftly smooth things over and return to the status quo, something that is of course in their favour,' one official said from Seoul.
'But it is not that simple. They have to understand that this is a massive issue for South Korea, even bigger than a nuclear test. Forty-six naval sailors have been killed. This is an act of war that demands a robust response,' the Seoul official said.
'Our public are shocked and enraged and no one can blame them ... this issue cannot simply be left to quietly go away, because it won't.'