After defeating Khwarazm in 1221, Genghis prepared his armies to punish Western Xia for their betrayal, and in 1225 he attacked with a force of approximately 180,000.
Genghis prepared his armies. This was to punish Western Xia for their betrayal. Genghis was defeating Khwarazm in 1221. He attacked with a force of approximately 180,000. This was in 1225. This was after defeating Khwarazm in 1221.