He joined the Prussian Army in 1903 as a member of the 72nd Field Artillery Regiment (stationed at Danzig), served in World War I, and remained in the Weimar-German Reichswehr.

[1] In 1936, von Rabenau was assigned by the then head of the general staff, Generaloberst Ludwig August Theodor Beck, to establish (from the Reichsarchiv) the first central archive of the German army, in Potsdam.

[2] As a Protestant Christian and a general, he successfully applied to then Reichsführer SS Heinrich Himmler for permission to take over Maria Laach Abbey, which had been seized from Roman Catholic Cardinal Graf von Galen in Münster.

Von Rabenau joined no resistance group, though he did act as a conduit between Generaloberst Ludwig Beck and Carl Friedrich Goerdeler, whom he knew from his time as an Abteilungskommandeur (Section Commander) in Königsberg (now Kaliningrad).

On 15 April 1945,[4] without having been charged or tried, General von Rabenau, one of the last inmates remaining in the Flossenbürg concentration camp, was shot on Himmler's specific orders.