This is where his younger brother, Gustav Konstantin von Alvensleben, was already living, who had worked his way up from a simple workman to become a successful entrepreneur.

During World War I von Alvensleben was awarded the Iron Cross 1st Class, later he became an orderly officer in the Army Group Gallwitz, aide-de-camp to Hermann von Eichhorn, the military governor of Ukraine, and finally personal aide-de-camp of the Kaiser to Pavlo Skoropadskyi (1873–1945), the Hetman of Ukraine, in Kiev.

In June 1930 the Deutscher Bund zum Schutz der abendländischen Kultur (German Union for the Protection of Occidental Culture) was founded and he became its president.

Prior to the "Night of the Long Knives", the purge of the SA leadership around Ernst Röhm and the conservative opposition on 30 June 1934, a hunting companion of earlier times, Graf von Helldorf [1], a member of the SA and one of the organizers of the purge (who eventually turned against Hitler and was executed after the 20 July plot) warned von Alvensleben to spend the coming weekend at his hunting lodge, as he then did, escaping certain assassination; it was thereupon that he was first condemned to death.

At Buchenwald concentration camp he was tortured, especially for the following incident, relayed by his grandson, Michael Roloff: A guard asked whether he, A., still placed people in classes.

Later on he had contact with Carl Friedrich Goerdeler and Ludwig August Theodor Beck via Hammerstein and was—as Rudolf Pechel writes in his book Deutscher Widerstand (German Resistance)—partially privy to the coup plans at the end of 1941.

At the trial before the Volksgerichtshof on 1 February 1945 it was not possible to prove that he had known about the assassination plans, but he was sentenced to two years’ imprisonment for defeatist statements made during a tea party in August 1943, whereby his age and failing health mitigated the punishment.