In German East Africa, at Bennigsen's suggestion, the "hut tax" was introduced in 1897, the ruthless collection of which led to countless uprisings among the local population in the following years.

[3] On 1 April 1899, Bennigsen was appointed the first governor of German New Guinea and the island area of the Carolines, Palau and the Marianas.

[5] In June 1900, Robert Koch was a guest of Bennigsen in Herbertshöhe during his New Guinea expedition to research malaria.

Whether for political or health reasons remains unclear, but on 10 July 1901, Bennigsen ended his service in German New Guinea by handing over the governorship to Albert Hahl.

In 1902 Bennigsen became a board member of the German Colonial Society for South West Africa [de].