What were some reasons for Genghis khans attacking northern china?

Genghis Khan attacked Northern China primarily to expand his empire and secure resources such as grain, wealth, and manpower. The region was strategically important for trade and military logistics, providing access to the rich markets of the Chinese civilization. Additionally, the Khitan and Jurchen states in Northern China posed a threat to Mongol territories and were seen as rivals to be subdued. Finally, the desire for revenge against previous conflicts and the goal of establishing Mongol dominance in the region also motivated his campaigns.