South China Sea: World War III?

Japan had mobilized some of 800,000 troop in the world war I and 37,000,000 soldiers at the world war II. How much troop needed in the world war III?

Let say that surface of South China Sea is 3.5 million square kilometer, it should be 3,500,000,000,000 m2 and absolutely needed  35,000,000 troop (1 soldier/100 m)