[3] He then performed his mandatory military service with the Royal Prussian Army as a one-year volunteer with the 5th (Westphalian) Uhlan Regiment, headquartered in Düsseldorf.

[4] Halfern obtained an entry level legal position with the Prussian civil service at the Düsseldorf Regierungsbezirk (Governmental District) in February 1900.

He then took a leave of absence and undertook a study trip around the world, which took him to Canada, the United States, Mexico, Japan and China.

After the end of the First World War and the conclusion of the Treaty of Versailles, Halfern was given the title of Administrative President for the French-occupied Territory of the Saar Basin by the Prussian Interior Minister on 2 October 1919.

On 1 October 1922, Halfern succeeded Wilhelm Kutscher as Regierungspräsident in the Hildesheim Regional District, serving until 1 April 1927.