What's the function of quoting Cao Cao's short sentences in Red Cliff Fu?

There are few stars on the moon, and birds fly south. One is to write about the beauty of moonlight, paving the way for Su Shi to linger under the moon and admire the selflessness of the creator; Secondly, Cao Cao is a hero in the world. He is thirsty for talents and has made great achievements, but it is only a moment to express the sadness of life. Third, traveling in Chibi and thinking about Cao Cao are just people, which is in line with the system of the article.