I'll recycle an old post of mine on why it's hard to see the Nazis ultimately siding with China over Japan:
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There is an interesting chapter entitled "Falling Between two stools: Nazi Germany's East Asian Policy" in Christian Leitz, *Nazi Foreign Policy, 1933-1941: The Road to Global War* (2004) where he notes that the Third Reich's originally friendly relations with China had their roots in the Weimar Republic. Both Germany and China (even though the latter was nominally one of the victors) considered themselves treated unfairly by the peace settlement. As early as 1921 the Chinese Republic reestablished diplomatic relations with Germany, and "Influential groups among Germany's business community, but also within the Reichswehr and the Foreign Ministry, both advocated and actively pursued an improvement of Germany's relationship to China. In the military sphere, this resulted in the highly controversial dispatch of German military advisers to Nanking in 1928, while in the economic field, German-Chinese trade relations expanded even during the Depression with a growing number of German companies establishing a presence in the country. From seventh place among Germany's export markets in 1929, China was to rise to third place seven years later." (p. 127) Japan, OTOH, was seen as a party to the oppressive Versailles Treaty (and as late as the early 1930s Japan failed to provide any support for the efforts of the Papen and Schleicher governments to reduce the military restrictions imposed on Germany by that treaty). German industrialists also complained about Japanese competition, Japanese copying of German goods, etc.
For the first few years of the Third Reich, Hitler showed little interest in Far Eastern affairs, and the Foreign Ministry, headed by Neurath, tried to maintain a "balanced" policy toward China and Japan. (For a short period in the mid-1930s the chief military adviser to Chiang Kai-shek was none other than Gerneral Hans von Seeckt, one of the Reichswehr's leading officers during the 1920's.) Ribbentrop was the man who made the most strenuous efforts (even before he became Foreign Minister) to redirect the focus of German Far Eastern policy away from China and toward Japan, with whom he sought a real military alliance, not just the largely propagandistic Anti-Comintern Pact.
So the question is: Without Ribbentrop, would Hitler still have changed Germany to a pro-Japanese orientation as he did after the outbreak of the Sino-Japanese War and especially from 1938 onward? (In 1938, the German ambassador was recalled from Peking and German representation was reduced to the level of chargé d'affaires; Manchukuo was officially recognized; and most important, German military advisers were recalled--although a small number resisted Nazi pressure and remained.) I think the answer is Yes, because once China lost most of her largest cities to Japan it was apparent that she could not do much for Germany economically. Moreover, she was obviously too weak--fighting for her own survival--to be of any military assistance. Japan, OTOH, was in a position to exert pressure on the Soviet Union (and to some extent on Britain and France through their colonies in the Far East) in peacetime and perhaps to be a German ally in case of war. Also, "The growing realisation that Britain would not conveniently fall into the position of ally 'alloted' it by Hitler reduced his concerns about antagonising the British when endorsing Japan's aggression in Asia." (p. 136)
As Leitz notes, even after 1938 German-Chinese relations--even military relations--did not completely cease. For example, arms shipments were gradually curtailed after November 1937, but not stopped entirely: "For a time, and against Ribbentrop's express wishes, Goering remained clearly too keen to let the lucrative war material trade with China expire. When Goering finally ordered the cessation of arms exports to China in April 1938, contracts concluded prior to August 1937 were exempted...As late as 15 October 1939 Goering indirectly acknowledged that such exports had not yet ceased when he told Sven Hedin that 'we are not at all interested in the China of Chiang Kai-shek. We have furnished it with war materiel but are now going to stop these supplies.'" (p. 135) Furthermore, Germany did not break all diplomatic relations with Chiang's government until 2 July 1941. (p. 134)
So Germany did not entirely eliminate relations with China, but there is no doubt that from 1938 on her basic orientation was toward Japan, and in view of the disparity in power between Japan and China, it is hard for me to see Hitler deciding otherwise, even without Ribbentrop. The only POD would be a much stronger China and weaker Japan, and that is not something which German policy in the 1930's would be able to bring about.
