Also known as the ocean Battle of Yashan, this battle happened in 1279 AD. The Song Dynasty army and the Mongol army had a large scale naval battle in Yashan. It was a rarely seen naval battle in ancient Chinese history.
As this battle directly concerned the survival of South Song, it was also the final battle between Song and Yuan.
The result was that the Yuan army won whilst being outnumbered. When South Song was wiped out, Lu Xiufu carried the young emperor Zhao Bing and jumped into the ocean to commit suicide. Many loyal officials died with them as well, along with 100 thousand troops and civilians.
After this battle, the Zhao Song Dynasty totally collapsed. At the same time, it meant that Yuan had unified China.
At this point, this was the first time China was conquered by the northern nomadic tribe.
The destruction of South Song was not a simple changing of dynasty but the wiping out of an entire country, signaling the end of ancient China. Some people felt that this battle signified the weakening and fall of Chinese civilization.
The Battle of Yashan caused Chinese civilization, which had survived for thousands of years, to stop. As a result, it had long and wide implications. The following Ming and Qing Dynasties also became largely different.
The destruction of the Song Dynasty caused their first try at changing from an agricultural society to a business society to fail. It was because the Song Dynasty tried this that their military power became weak.
Along with the destruction of South Song, the progress of China was halted. The once highly advanced economy, culture, technology, and the like were restricted by the emperor and the political structure and the like were all affect. The backward Mongol people of the Yuan Dynasty started to consolidate their power, closing borders and reducing trade. They started to focus on Neo-Confucianism. Following which, the Ming Dynasty that usurped them chose to seal themselves off.