This would surely start a World War.
Doesn't that depend on there being a worldwide system of alliances that the PRC can call upon?
to be fair, the entire world against China would still be a "world war"
unless, maybe, nah...couldn't be.....UNLESS! he thinks world powers like Cuba, Venezuela and Syria would join in and bring in their powerful armies and totally tilt the game in favor of the Red Chinese.
In a situation where India gets involved--which doesn't totally make sense for a variety of reasons--I can see Pakistan joining the fray, but Russia's interests do not appear served at all by coming to China's aid when the bulk of its population, defense needs, and strategic aims are on the other side of the continent; and, so far as I am aware, they are
partners, not
allies.