A) World War III already happened. It was called the Cold War.
B) Wars like WW1 + especially 2 likely aren't possible in the conventional sense any longer.
C) China + Russia would get bent over if they tried to take on the US + UK + France + Germany + Japan + Canada + rest of NATO + likely India (has adversarial relationship with China) + South Korea + Australia. Their economy would take a massive hit. Some little island isn't worth all that trouble IMO. I'm guessing they are smart enough to realize the answer is no. Let the status quo be.