Reichenau was born in Karlsruhe to a Prussian general and joined the German Army in 1902. During World War I he served on the Western Front. He was awarded the Iron Cross First Class and by 1918 had been promoted to the rank of Hauptmann.
Reichenau stayed in the army under the Weimar Republic as a General Staff officer. From 1931 he was Chief of Staff to the Inspector of Signals at the Reichswehr Ministry, and later served with General Werner von Blomberg in East Prussia. His uncle, an ardent Nazi, introduced him to Adolf Hitler in 1932 and von Reichenau became a convert, joining the Nazi Party soon after. Doing so was a violation of army regulations, which forbade army members from joining political parties.
Reichenau's family was quite wealthy, descended from a long line of German nobility. Throughout the nineteenth and early twentieth centuries the von Reichenau family owned and operated one of the largest furniture factories in Germany. In 1938, records indicate that the family "donated" the factory to the Nazi cause, transforming it into a munitions plant. During Allied attacks in 1945, the factory (located just outside Karlsruhe, Germany) was destroyed in an air raid, the last remaining vestiges of the von Reichenau family's wealth and prominence obliterated in the process.
When Hitler came to power in January 1933, Blomberg became Minister of War and von Reichenau was appointed head of the Ministerial Office, acting as liaison officer between the Army and the Nazi Party. He played a leading role in persuading Nazi leaders such as Hermann Göring and Heinrich Himmler that the power of Ernst Röhm and the SA must be broken if the Army was to support the Nazi regime. This led directly to the "Night of the Long Knives" of 30 June 1934.
In 1935 von Reichenau was promoted to lieutenant-general and was appointed Commander in Munich. By 1938, after the Blomberg-Fritsch Affair in which General Werner von Fritsch was forced out of the Army command, von Reichenau was Hitler's first choice to succeed him, but older leaders such as Gerd von Rundstedt and Ludwig Beck refused to serve under him, and Hitler backed down. Von Reichenau's enthusiastic Nazism repelled many of the generals who would not oppose Hitler but who did not care for the Nazi ideology.
In September 1939, von Reichenau commanded the 10th Army during the invasion of Poland. In 1940 he led the 6th Army during the invasion of Belgium and France, and in July Hitler promoted him to field marshal.
During the invasion of the Soviet Union in June 1941, von Reichenau again commanded the 6th Army, which captured Kiev and Kharkov. Politically, von Reichenau was an active anti-Semite and supported the work of the SS Einsatzgruppen in exterminating the Jews in the occupied Soviet territories. He encouraged his soldiers to commit atrocities against the Jews, telling them: "...In this eastern theatre, the soldier is not only a man fighting in accordance with the rules of the art of war...For this reason the soldier must learn fully to appreciate the necessity for the severe but just retribution that must be meted out to the subhuman species of Jewry...".
A few historians such as Walter Görlitz have sought to defend von Reichenau, summarizing his October 1941 "Reichenau Order" as "demanding that the troops keep their distance from the Russian civilian population." Actually, the order included such directives as killing any Russian civilian found travelling without a permit and away from his home village (see external links below).
For this reason von Reichenau was one of Hitler's favourite generals. On 19 December 1941 Hitler sacked Walther von Brauchitsch as Commander-in-Chief and tried to appoint von Reichenau to the post. But again the senior Army leaders rejected von Reichenau as being "too political" and Hitler appointed himself instead.
In January 1942 von Reichenau suffered a cerebral hemorrhage, and it was decided to fly him to a hospital in Germany. He is often said to have been killed in a plane crash in Russia, though Görlitz writes that the plane merely made an emergency landing in a field, and that von Reichenau actually died of a heart attack.
It is believed Reichenau is survived by relatives currently residing in the United States. After the fall of Nazi Germany and the dissolution of his once-noble family's wealth, Reichenau's daughter and grandchildren, sister, or according to some claims, both emigrated to the US. The location and names of von Reichenau's existing family are supposedly a closely guarded secret.