German WWI Feldpostkarte.
Kriegerfriedhof (Military Cemetery) in Bobroniec bei Bartoszonka (Russland).
Angelege von der Sanitäts–Komp. / 1. Korps.

Scarce Feldpostkarte, militaria example from the German Eastern Front.

On mobilization, I Corps was assigned to the 8th Army to defend East Prussia, while the rest of the Army executed the Schlieffen Plan offensive in August 1914. It saw action at the battles of Stallupönen, Gumbinnen, and Tannenberg, and the First Battle of the Masurian Lakes.
The Corps was still in existence at the end of the war.