Oster was the son of Oberstleutnant Heinrich Oster and served as a volunteer for a year in the army himself in 1898 before studying chemistry at the Berlin-Charlottenburg Technical Academy and the Friedrich Wilhelm University in Berlin, obtaining his doctorate in 1905.
Technical University of Berlin.
He immediately went to work for Agfa and remained with them until 1914 when he returned to the army to serve in the First World War. He was promoted to full membership of the board at in 1931. Oster recognised the potential for growth of the Nazi movement and was one of the first leading figures in to advocate close co-operation with Adolf Hitler"s movement.
Oster held sponsoring membership of the Schutzstaffel from 1935 to 1939, a position which entitled him to officer rank in the black uniformed movement.
Oster was arrested by the occupying American forces in 1946 and the following year was charged with war crimes as part of the trial. In 1948 he was sentenced to two years imprisonment for "plunder and spoliation".
Following his release in 1949 he took on a position on the board at Gelsenberg AG.
Oster was wounded early in the war, losing his left eye as a result, and so most of his service as a member of staff to the Commander of the German Army in Alsace, as well as in matters of arms procurement to Badische Anilin- & Soda-Fabrik. Following the armistice Oster was hired full-time by Badische Anilin- & Soda-Fabrik as a deputy director and he was made a member of the board in 1921. He did not become a full member of the Nazi Party itself until 1940.
