During the Japanese invasion of Manchuria, the ‘North Korean Route’ connecting Manchuria and Japan on which artillery was transported served as a pipeline for the exploitation of physical resources. The ‘North Korean Route’ was designed to connect the Manchurian and Chosŏn railways to the three ports of North Korea. Ships and vessels sailing from these three ports in North Korea could arrive at various ports in Japan by crossing the East Sea. The Japanese colonial government was aware of the importance of this North Korean route well before it even began to plan its invasion of the Chinese mainland. Having begun to construct railways in North Korea in the aftermath of the Russo-Japanese War, Japan completed the Hamgyŏng Route in 1928. It also completed the Jilin-Dunhua Railway in Manchuria. The importance of the three ports in North Korea connected to the Jilin-Hoeryŏng Railway and Dalian became even more evident in the aftermath of the Manchurian Incident of 1931. The Japanese military established plans to dominate transportation networks in Manchuria that revolved around the establishment of the two largest harbors in the area. The Chinese Eastern Railway (CER) managed by Russia sound found itself to be a direct competitor to the proposed ‘North Korean Route’. The Manchurian economy had long been divided into the zones occupied by the conflicting Chinese Eastern Railway and Southern Manchurian Railway zones. Russia, which had established a policy of avoid conflicts with Japan and Manchukuo, sold the Chinese Eastern Railway (CER) to Manchukuo when the profitability of the latter began to decline. This in essence marked the integration of the East and South Manchurian economies. Under these circumstances in which Japanese and Chosŏn resources flowed into Manchuria, the influence of Harbin decreased as North Manchuria became a rear base for the ‘North Korean Route’. The three ports of North Korea played an important role in the implementation of the theory of the unity of Chosŏn and Manchuria that was heavily promoted at the time. They competed with each other to become the terminal port of Jilin-Hoeryŏng Railway and also cooperated with one another in resolving pressing issues in the region. Competition and conflict did however surface between the provinces and military authorities of Japan, Manchukuo and Chosŏn. In addition, a competition also emerged between the three ports of North Korea over regional development. Nevertheless, the economic cooperation network based on the ‘North Korean Route’ and ‘three ports of North Korea’ continued to function until the collapse of Japanese imperialism.