Sino-German cooperation in the 1880s

Germany did build two ironclads for China. Though they delayed delivery so the French wouldn’t have to face them in the Sino-French War.

In that conflict perhaps some Schwartzkoff torpedoes (and better trained operators) might have made a difference.
 
This might accelerate the consolidation of Russia's rivalry with Germany and her focus on affairs in the Balkans rather than distractions in the Far East (the latter of which the Kaiser eagerly encouraged IOTL). Whether or not China, now modernizing its military and industry with more success, would actively join the Central Powers in case of war is another question, however, seeming as her interests wouldn't be many besides securing some buffers at border regions.
 
This might accelerate the consolidation of Russia's rivalry with Germany and her focus on affairs in the Balkans rather than distractions in the Far East (the latter of which the Kaiser eagerly encouraged IOTL). Whether or not China, now modernizing its military and industry with more success, would actively join the Central Powers in case of war is another question, however, seeming as her interests wouldn't be many besides securing some buffers at border regions.
I don't know about China for sure but there were contacts with Siam in that time period, and deep fears of the Indochina colonial establishment of Prussian involvements in the highlands.
It's however worth noting that Germany had no qualms getting bits of China, such as Tsing Tao
 
It would be suicidal for China to join the Central Powers. They have British India, French Indochina and Hong Kong on their southern border and Russia on their western and northern borders. As soon as they declared war, they would be invaded from both sides.

Also, Germany was already helping the Qing Dynasty with modernization, at least where the military was concerned. Many Chinese cadets went to Prussia to study it's military and the Qing army also used some German-made equipment.

Any sort of increased assistance to China would hit a snag named Kaiser Wilhelm II. He referred to East Asians as 'yellow monkeys' and much like most Europeans of his time, feared the 'Yellow Peril'. I don't see the Kaiser giving a potential enemy like China any assistance whatsoever. Correct me if I'm wrong.
 
While, I'm not sure about joining the central powers, should China be able to industrialised early enough, the imperial powers won't have long in China, as they will have lost their main advantage over it.
 
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