Not so China. The world would have its say as to weather South Korea broke the armistace and invaded the north, vs China again comming to the aide of their beleagured North Korean friends.

Don't expect western media to be sympathetic to the US or South Korea.

Chinas military is shrinking in size people wise, and growing dramatically in training,(they now take only the best and brightest, because of the 'huge' selection base and the decent pay). Modern aircraft, weapons, missles, communication systems, and equipment such as armored vehicles, tanks, artillory, and numerous heavy weapons are already in the inventory or are being built in China.

They will not go into battle with canvas shoes and not enough weapons and no food, radios or communication, such as during the Korean war of the 1950's. They will go into North Korea well trained, fed and supported, to a very mountainous terrain that will favor the defender. They build many of their own weapons and do not use the "AK47".

The Chinese fighters 'who have always been brave and courageous fighters' will dig their tunnels, sneak up at night, and use their patriotism, to overwhelm any mediocre adversary. Their country and public will support them as they have a tightly controlled media. Ours will not.

They 'may' lose in the end militarily, but they have a history of turning world opinion to their side propoganda and political wise. The US has a poor track record in those areas.

The US and South Korea may "win" a war with China over North Korea, but it will be very, very, bloody and at great cost financially, militarily, and politically.

Basically this means it would be impossible to win against them in a ground war, but they lack the ability to strike back or cause significant damage to the US. Basically they just sit there until we're tired of fighting them, then we go home, then they can call it a victory. But insofar as actually attacking the US can causing damage, they are not able to do that with conventional weapons. And they just recently gained ICBM nuclear capacity, something we've had for decades. And a nuclear war is the last thing China wants.

Collapse can take many forms, including infighting or rebellion. The Chinese need not invade so much as support the insiders of their choice or the rebellion from the outside, depending how they see the situation.

Support can include military intelligence, volunteers from China of Korean ancestry, as well as food, fuel and arms (weapons, ammunition, tanks, even air support). Yet no "Chinese" troops would cross the border.

Then what?