Hilmar was born in Hanover on 31 January 1867, and belonged to the ancient von dem Bussche noble family which originated from the County of Ravensberg.

His mother, the widow of Charles Frederick Rocheid of Inverleith (1831-1864), was a daughter of Peter Heinrich August von Salviati (1786-1856), the Prussian Ambassador to Spain.

In May 1895, he was appointed as legation secretary to the German embassy in Tangier, replacing the incumbent envoy Christian von Tattenbach, before becoming chargé d'affaires in August 1895.

[3] He left Argentina a year later and was assigned to Egypt, working at the German embassy in Cairo on 26 February 1900 under chargé d'affaires Maximilian von Loehr.

In December 1915, Bussche-Haddenhausen was appointed Envoy but had to return to Germany at short notice in the summer of 1916 because of the unexpected break in diplomatic relations with Romania.

[9] In August 1919, he was reported to have said that "the indemnities provided for in the Peace Treaty will never be collected, because they are so ridiculous and high that the League of Nations will eventually annul or reduce them.

By 1928, however, he held the office of chairman of the Verein für Deutsche Kulturbeziehungen im Ausland (Association for German Cultural Relations Abroad), serving until 1931.