Oberg worked for a tropical-fruit trading company before enduring a long period of unemployment. In 1930 he acquired a tobacco stand in Hamburg.
In 1938 Oberg was given command of an SS (Schutzstaffel) battalion in Mecklenburg. The following year he became chief of police in Zwickau.
On the outbreak of the Second World War Oberg went to Poland and became SS and Police Leader in the Radom district where he was responsible for rounding up Jews and the drafting of Poles for forced labour.
In March 1942, Oberg was promoted to SS-Brigadeführer and two months later was posted to Paris where he became SS and Police Leader in occupied France. In this position he brought in severe measures to deal with the French Resistance including the shooting of hostages. Oberg was also responsible for applying the Final Solution in France. This action resulted in 75,000 Jews being deported from France to extermination camp in Nazi Germany and Poland.
Oberg was promoted to SS-Obergruppenführer and police general in August 1944. Later that year Oberg was posted to the command of a military unit that was part of an army formation commanded by Heinrich Himmler.
In June 1945 Oberg was arrested by Allied troops. The following year he was extradited to France where he was brought to trial. Convicted of war crimes, Oberg was sentenced to death on 9th October, 1954. After an appeal, this was reduced to life imprisonment.