Minister Frans Erasmus embarked on a process of ridding the Defence Force of officers associated with the Smuts government and replacing them with others whom he considered more Nationalist, one which Afrikaners would feel more at home. In 1952, Erasmus posted Brigadier Pieter de Waal as a Military attache to the United States, replacing him with Biermann, one of only seven Afrikaans officers in the navy in 1948. Then Commander Biermann was appointed Naval and Marine Chief of Staff (the head of the navy) on 1 December 1952, and promoted to the rank of commodore, jumping two ranks. During his tenure the Simonstown Agreement was signed on 30 June 1955. He held commodore rank until 1 April 1957, with the handing over of the Simon's Town Naval Base, he was promoted to rear admiral. Biermann was made vice admiral on 1 December 1965, when his position was simultaneously retitled as Chief of the Navy.