I’m currently taking an Asian Studies class on modern Chinese culture and history. We just started learning about the Sino-Japanese War, which began in 1937 before being enveloped into the larger World War II in 1939. Our professor made the point that despite Germany and Japan being allies during the war, when Japan invaded China, the Nazis actually opposed the Japanese attack because Germany had friendly relations with the Chinese Nationalist government (aka the KMT) led by Chiang Kai Shek.
The Chinese government under Chiang Kai Shek desperately wanted to modernize itself as China in the 1930’s was still a very underdeveloped nation compared to Europe, America, and Japan. China turned to Germany for assistance in industrial and military modernization. The Nazis sent military advisors to train the Nationalist army and German businesses started operations in China, building railroads, bridges, roads and modern factories. In return, the Nazis received vital raw materials and natural resources from China that Germany needed to rebuild its economy and military. There was even a bond established between the KMT and the Nazis, since the Nationalists were fighting the Communists for control of China while the Nazis despised the Communists. This shared hatred led to friendly relations throughout the 1920s and 1930s.
So when Japan invaded China in 1937, Germany wasn’t too pleased. They had a lot of business and military interests invested in China and their supply of raw materials coming from China was now at risk. However, Hitler was not eager for Germany to entangle itself in the Far East and instead tried to mediate a truce between Japan and China. But when that failed, Hitler had a choice as to which side he would back. He eventually backed Japan because he saw them as far more militarily superior and would be a worthy ally to take on the Soviet Union. Thus, this ended all Sino-Germany cooperation until after World War II.