The sea battle of Yashan in Song Dynasty led to the traditional Han regime being completely replaced by the nomadic dynasty in the north for the first time. This sentence is used to indicate that after the destruction of the Song Dynasty by the Yuan Dynasty, China culture suffered a serious fault and China classical culture was destroyed.
Historical background:
The Battle of Cliff Mountain, also known as the Battle of Cliff Gate, was a battle between Song Jun and Yuan Army in the late Southern Song Dynasty. This war marked the demise of the Southern Song Dynasty. There are two versions of China's participation in this war: 300,000 and 500,000. However, according to Japanese records, the Song and Yuan Dynasties invested more than 500,000 troops (including 200,000 in the Song Dynasty, but these 200,000 people included civil servants and their families, court personnel and ordinary people, and their actual combat effectiveness was only tens of thousands). In the end, Song Jun's battle marked the demise of the Song Dynasty.