Oskar Karl Gustav Adolf was born in the Potsdamer Stadtschloss, on 27 July 1888 and was the fifth son of Wilhelm II, German Emperor, and Augusta Victoria of Schleswig-Holstein.
During the First World War, Oskar served as a colonel in the Konig Wilhelm I Grenadierregiment and he was given the Iron Cross, Second Class, for his bravery and leadership during an attack in Belgium. A month later, Oskar led his men into battle at Verdun in 1914 and was awarded the Iron Cross, First Class. Oskar collapsed on the field and spent the rest of the year recovering from a heart condition, however he eventually returned to duty and served on the Eastern Front. After the war, Oskar was listed amongst others in the imperial family as being a war criminal and was condemned for applying for a colonel’s pension from the Weimar Republic.
On 31 July 1914, Oskar married Ina Marie von Bassewitz in what was initially a morganatic marriage, however Ina Marie was granted the title of Countess von Ruppin a few days before the wedding. The marriage was decreed to be dynastic in accordance with the laws of the Royal House of Hohenzollern on 3 November 1919 and Ina Marie was henceforth styled as a Princess of Prussia. The couple had four children, three sons and a daughter, although the eldest, Oscar, was killed in action the Second World War.
With the monarchy abolished, Nazism was on the rise and Oskar was commissioned as a Generalmajor zur Verfügung, however his enthusiasm waned when it became obvious Hitler had no intention of restoring the kaiser to the throne. The Nazi Party began to be suspicious of the imperial family due to their renewed popularity in Germany and they had their commissions revoked as a result. Public sympathy had increased in the wake of the deaths of two of the former kaiser’s grandsons, as well as Oskar’s eldest son being killed in Poland in September 1939, Oskar’s nephew, Wilhelm, son of the former crown prince, had been killed in France in May 1940.
Oskar’s health declined during his final years and he died of stomach cancer in a clinic in Munich on 27 January 1958.