Hangu Pass
In 205 BC, after conquering the Guanzhong region, Liu Bang advanced to the east of Hangu Pass to prepare for an attack on the Henan region. Sima Xin, the King of Sai, Dong Yi, the King of Di, and Shen Yang, the King of Henan, surrendered to Liu Bang. Zheng Chang, the King of Hán, refused to submit to Liu Bang so Liu Bang sent Han Xin to attack and defeat him. Liu Bang then replaced Zheng Chang with Hán Xin as the new King of Hán. Zhang Er, the former King of Changshan, joined Liu Bang after losing his domain to Zhao Xie and Chen Yu.