Why did the Song rulers withdraw to the south?

Answer 1

The Song rulers withdrew to the south in the 12th century due to invasions by the Jurchen people, who eventually captured the northern capital of Kaifeng in 1127. This forced the Song rulers to retreat to the southern capital of Hangzhou, where they established the Southern Song dynasty. The Jurchen went on to establish the Jin dynasty in northern China, leading to a divided China during this time period.