If world war three will happen on this coming end of the year maybe those country that support us who bomb recently Syria and Afghanistan will be declared a war those who are not supported like china and Russia. They will like killing those innocent people around them.
At the moment I see no reason why China entered the war. Where America is opposed to the interests of China? Only in Economics, but this is an economic war and it is a long time and never stops. Russia is very weak state to fight with America. Russian can only secretly support the enemies of America and Europe. In open confrontation they will not go.