After the Lugou Bridge Incident in 1937, the War of Resistance Broke Out in full swing. The Japanese quickly occupied China's coastal ports such as Tianjin and Shanghai, basically completing the blockade of China's maritime traffic. Since then, cutting off land passages has become a major part of Japan's strategic blockade. However, in the years that followed, China still imported a large amount of materials and arms from overseas through the international passage of the northwest and southwest rear areas.
As far as the land route is concerned, there are three main transport routes to foreign countries that China can use at that time.
The Sino-Soviet Land Passage
From Lanzhou, Gansu, through Xinjiang, to the territory of the Soviet Union, a total length of 1700 miles. In the early days of the War of Resistance Against Japanese Aggression, the Soviet Union supported China's arms and materials, and some of the materials that China transported to the Soviet Union for exchange passed through this road. However, the passage was a long way away, and the geographical and climatic conditions along the way were not good, so that only a small part of the soviet supplies were imported into China, and most of the supplies were transported by sea from the ports of Southeast Asian countries to Chinese mainland.
Yunnan-Vietnam Railway
The road runs from Kunming, Yunnan, through the Lao Estuary, into Hanoi, Vietnam, to Haiphong. Vietnam was in the French sphere of influence at the time and had always supported China's transportation of supplies. However, after the outbreak of the European War on September 1, 1939, the French gradually began to soften their attitude toward Japan in order to deal with fascist Germany with all their strength. On September 23, the French governor announced to the Chinese consulate in Hanoi that Chinese arms, automobiles, and gasoline would be banned from transiting through Vietnam, and that stocks that had already arrived would be in a limited period of time. Later, after the Chinese side negotiated with the French side, the French government privately agreed that the goods "are as old as ever, and in fact there will be no difficulties." Later, with the occupation of France by the Germans, this private cooperation also stopped completely.
Burma Highway
Built from the outbreak of the War of Resistance against Japanese Aggression to December 1938, the road is a veritable 1,146-kilometer anti-war highway that stretches from Kunming, the capital of Yunnan Province, to Lashio, the end point in Burma, and then connects to Yangon, Myanmar's largest port, by road or narrow gauge railway. Since July 1940, when communications through Vietnam were cut off by the Japanese army, all the strategic materials purchased by China from abroad had to be transported into China through here, so both military and civilian movements were quite frequent, with 300 to 800 cars coming and going every day.
In order to cut off this important line of communication, the Japanese army repeatedly protested and demanded to the British side, and the British side also made a compromise and closed the Burma Road for 3 months. However, under the joint pressure of China and the United States, it opened up again and undertook more heavy transportation tasks, with more than 8,000 transport vehicles coming and going every day at the most stressful time. Seeing that diplomatic blackmail was ineffective, the Japanese simply began to use force, dispatched troops to Burma in early 1942, and occupied Rangoon on March 8 of the same year, interrupting Sino-Burmese communications.
Since then, Western aid to China can only be transported by air channel.