Li Hongzhang and Zuo have always been at odds. Li Hongzhang once wrote to Zeng Guofan and said, "The true face of Zuo Gong is revealed here." They are all disciples of Zeng Guofan, but everyone knows that they have been playing for decades. So what caused their disagreement?

First of all, they don't like each other. According to folk rumors, Zuo has been to Li Hongzhang, and Li Hongzhang came out late. Recalling the rumor that Li Hongzhang dotes on his youngest wife, Zuo couldn't help sneering, "Wash your feet with your wife." . Li Hongzhang blurted out without weakness, "I have a scholar background" and told Zuo about his heart disease. He is only a juren, but he has no reputation as a scholar. As a result, the two of them walked around from now on.

Second, the bitterness deepened. After the Taiping Heavenly Kingdom was suppressed, Zuo and Li Hongzhang led Chu and Huai armies to pursue the Nian army in North China. 1August, 868, Nian Jun Zhang Zongyu was completely annihilated. After the war, the Huai army ranked first in meritorious service, and Li Hongzhang was promoted to assist the university students. Zuo Tang Zong doubted Li Hongzhang's statement about Zhang Zongyu's suicide, so he led an army to search everywhere. Li Hongzhang was furious and wrote to Zeng Guofan saying, "(Left) A Shen's true face is revealed here." The two unhappy people became more hostile.

Third, different political views, fighting for coastal defense and blocking defense. In the face of threats from the sea and the frontier, how did the Qing Dynasty allocate limited strategic resources to the eastern coast and the northwest frontier? Li Hongzhang advocates strengthening coastal defense and guarding against rising Japan. Left mainly solved the urgent need of Agubo's invasion and curbed the arrogance of Russia and Britain who coveted Xinjiang.

Facing the urgent need, the court favored Zuo's suggestion. At that time, the average fiscal revenue of the Qing Dynasty was 80 million taels of silver a year. From 1875 to 1884 (that is, in the middle and late period of the left-west expedition), 80 million Liang of defense funds were spent. On the contrary, from 1885 to 1894, when the Sino-Japanese Sino-Japanese War broke out, the coastal defense funds were only 30 million Liang. From this point of view, the court still advocates that fortress defense takes precedence over coastal defense.