I know China and the kings of the east are not under his authority for they gather an army of 200 million men to attack the anti-Christ. Does God use them for his purpose to destroy the AC, or will God also eliminate this Army?
The only mention of a 200 million man army is in Rev. 9:15-16 during the sixth trumpet judgment which takes place before the anti-Christ is officially revealed. I believe it refers to a battle fought for control of the Far East. Two billion people will die because of it. Later in Rev. 16:12 the Kings of the East come to join the anti-Christ in the Battle of Armageddon. When the Lord returns at the end of this battle He destroys them all (Rev. 19:19-21).