Id be surprised if South Korea went all in with China.
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If South Korea doesn’t have large deposits of rare earths used in the manufacturing of electronics, China doesn’t want to own or have anything to do with South Korea, except maybe just enough to tweek our nose.
China’s moves in Africa and, more recently Greenland, are all about global control of the supply of rare earths for electronics manufacturing.
China and South Korea have one thing in common, a fear that if North Korea deteriorates, both countries would be flooded with millions of refugees they can’t handle.
China and S Korea might eventually go to war over the cobalt, manganese, nickel, copper and aluminum metal deposits worldwide to produce those lithium ion batteries that their tech companies are hedging bets on.
Reason enough. If South Korea decides they can't depend on us then China may be their only option. For South Korea, moving closer to China places China between them and North Korea. For China, South Korea is an affluent trading partner to sell to and buy from.