This is the order of battle for both the Russian and German armies at the Battle of Tannenberg, August 17 to September 2, 1914.
Hindenburg at Tannenberg, by Hugo Vogel
I Corps (German Empire)
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The I Army Corps / I AK was a corps level command of the Prussian and then the Imperial German Armies from the 19th Century to World War I.
Headquarters, about 1908