From 1868 he served as a lieutenant in the Grand Duchy of Baden field artillery regiment, with which he also took part in the Franco-Prussian War.
He trained a local police force loyal to the king and provided the king's supporters with weapons to protect the colonists from their opponents, and to crush protests against the newly imposed poll tax on the locals.
From 1 December 1889 to 15 April 1891, Brandeis was secretary at the Imperial Commissariat on Jaluit in the Marshall Islands, then deputy commissioner.
On 5 February 1892[4] Brandeis was appointed Chief Judge for the Eastern District of Bismarck Archipelago and the Solomon Islands of the Colony of German New Guinea.
In July 1893 there were riots due to the illegal expansion of the German New Guinea Company plantations.
During the dispute between the colonist Georg Schmiele [de] and Paul Kolbe, husband of "Queen Emma" in June 1894, Brandeis pointed out to the former his "duty" as an officer, namely to challenge Kolbe to a pistol duel at 15 m. In the same year he undertook another punitive expedition against the native population as a captain with other colonists.
Since 24 March 1898, he was Imperial commissioner for the Marshall Islands, where he arrived on 28 August, only four months after his appointment.
After her separation from Brandeis, Antonie lived in Hamburg and was instrumental in founding the Colonial Women's School in Rendsburg.