Left's efforts to establish a modern military industry are undoubtedly correct. First of all, Zuo inherited and developed the idea of "learning from foreigners to control foreigners" and put it into practice. During the First Opium War, Lin Zexu and others realized that it was impossible to fight abroad without cannons and ships, so they strongly advocated using the income of Guangdong Customs to build guns and ships. Unfortunately, there was no response from the ruling and opposition parties that day, which led to the decline of singing. Under the impetus of Lin Zexu's advanced thoughts and modern western industrialization thoughts, Zuo clearly saw the gap between China and the west in science and technology. Taking Japan as an example, he said, "We all benefit from the sea and have scruples about each other, but I have nothing. For example, if you cross the river, people will operate the boat and I will make a raft; For example, it is still a horse. People straddle the horse and I ride the donkey. Could it be? " It is pointed out that "Tessie is smart, but China need not be complacent. If Tessie has it, China cannot make it out of nothing". Emphasize the necessity of developing modern military industry.

Under the closed-door policy of the Qing Dynasty, what Zuo did was indeed far-sighted. Secondly, the establishment of military industry by the left met the needs of the domestic and international situation at that time. China was a semi-feudal and semi-colonial country in modern times. The invasion of imperialist powers at sea deepened the social crisis in China. Zuo realized that if the soldiers were not strong, the people could not be rich. "If you want to guard against the harm of the sea, you must organize the navy. If you want to organize a navy, you must set up a bureau to supervise the construction of ships. " "The ship is prosperous, the military and political affairs are difficult to solve, and the customs are prosperous." Under the impetus of Zuo et al., not only did modern military industry develop to some extent, but it also played a positive role in promoting the development of civilian industries such as mining, transportation, textiles and commerce. Third, the three modern military industries managed by the Left played an effective role in the war at that time, especially in resisting foreign invasion and defending the territorial sovereignty of the motherland. For example, in the war against Agubo Gang and the recovery of Xinjiang, the arms manufactured and repaired by Lanzhou Machinery Bureau were sent to the front line continuously. 1876 supplied 20,000 bullets to the Qing army at one time, which enabled the Qing army, which had been equipped with a considerable number of foreign guns, to "gain strength" in attacking the city and plundering the land.