What did Wu Xu and Song Lin discover from Yue Fei's military thought?

Wu Xu and Song Lin believed that when people talked about Yue Fei, they would think that Yue Fei was a model of running the army in ancient China, and "Yue Jiajun" became a model for a while. Wu Xu and Song Lin thought that although he didn't have a military treatise handed down from ancient times, it can be seen from his discussion of historical documents and military practice that Yue Fei's military thoughts were mainly based on his military background. However, Wu Xu and Song Lin found that Yue Fei was well educated by China's traditional education since childhood, and he was diligent and studious. Wu Xu and Song Lin also found that Yue Fei knew how to write calligraphy. Calligraphy is characterized by lines and grass, full of vigor and vitality, strong and unyielding, with an air of purity and integrity, and quite a temperament of a civil servant. When Wu Xu and Song Lin saw Yue Fei's calligraphy, they could feel the free and easy spirit between his lines.