You are so lacking in knowledge of history. But you have lots of Internet bravado.
You actually think the US could launch unprovoked strikes on North Korea, and China would stand idly by?
China does not want instability in North Korea. It risks US and South Korean troops on their border and tens of thousand of North Korean refugees flooding into South China.
China is trying to get both sides to ratchet down the rhetoric and work towards a peaceful solution.