Answer:
After obtaining Xiangyang (modern Xianfan) in 1273, the Mongols gained access to the Yangzi River — and the chance to penetrate deep into Song territory. More and more Song land fell into Mongol hands, and the government moved further south.
Step-by-step explanation:
The Mongols eventually defeated the Song land and naval armies and captured more than 100 ships. The Yuan dynasty created a "Han Army" (漢軍) out of defected Jin troops and an army of defected Song troops called the "Newly Submitted Army" (新附軍).