Throughout this time however, Temüjin continued to build his forces and by 1213 had an army so powerful that they conquered all of the Chin territory up to China's Great Wall. From this strategic location, Temüjin made the decision to split up his forces into three smaller armies in an attempt to break through the wall and finish his conquest of China. He sent his brother, Kasar, as the head of one of these armies east into Manchuria. He sent another army south toward Shan-si under command of his three oldest sons. Temüjin led the third army, along with his son Tuli, towards Shan-Tung. The plan was a success as all three armies broke through the wall in different places.
The battle for Beijing (Yenching) was long and tiresome, but the Mongols proved to be more powerful as they finally took the city in 1214, massacring its inhabitants. This opened the Yellow River valley to further Mongol ravages.