Born in Breslau, in what is modern-day Poland, Bräuer entered service in the German foreign ministry in 1920.

Until the invasion, the official German foreign policy was to respect Norwegian neutrality, a line which Bräuer is said to have agreed with and worked toward.

However, on the evening of 8 April 1940, the envoy received orders from Berlin — he was to be Hitler's representative and deliver a German ultimatum for the occupation of Norway to the Norwegian government the next morning.

In the following days, Bräuer tried to convince the Norwegian government and King Haakon VII to capitulate and to name Vidkun Quisling as prime minister.

On 16 April, Hitler recalled Bräuer from Oslo, deciding that the Norwegian resistance to the invasion dictated that the country be administered by a more authoritarian personality.