Korea is allied with US. After China got rich with their Made In China sales, China strengthened their influence in Asia. They claimed to dismantle THAAD in Korea, threatened Taiwan by force, and took over South China Sea by building many military sites. Now world is threatened by China, and this made US get closer to its Asian allies. Many measures have been made to counter China. Korea's new president Yoon Seok Yeol increased joint military drills with US and even with US and Japan. China on the other hand sees this imminent threat made by US and its allies, heading to be allied with Russia and North Korea. The hottest spot is Taiwan, the island claimed by China as their own territoty. China believes that Taiwan should be unified by China under Chinese communism, sending more military aircrafts and warships to threat Taiwan. US recognizes this and increases their military transits around Taiwan to warn China, telling US will defend Taiwan when they are under attack.