Kettmann was the eldest son of a businessman and worked for his father until the company was ruined by the
financial crisis of 1930, after which he worked as a journalist. He joined the NSB on 2 August 1932. On 12 October he married Margot Warnsinck; they had started the publishing house, De Amsterdamsche Keurkamer, only shortly before he joined the party, on 14 or 21 July, with the aim of promoting a new
völkisch ideology, which soon became specifically National Socialist. In 1939 the company published the Dutch translation of
Hitler's
Mein Kampf. In the years before World War II, in addition to running the company, he edited
Volk en Vaderland, the national weekly of the NSB (until 1941) and wrote and published prose, poetry and essays, showing enormous energy. Over the years his relation with Anton Mussert deteriorated, as Kettmann accused Mussert of being unable to grasp the true, revolutionary nature of Nazism. This led ultimately to his joining the
Nederlandsche SS on 7 March 1942. In September 1942 Mussert expelled him from the NSB; Kettmann was considered too radical a Nazi. He went to the
Eastern Front as a war correspondent. Back in the Netherlands, he was accused of: • joining the German armed forces, • aiding the enemy, Nazism and
antisemitism, • having written and published articles and poems glorifying National Socialism and antisemitism. He was sentenced to 10 years in prison. After his release in 1955 he refrained from any political activity. He published some volumes of poetry, in which he demonstrates not having lost his Nazi ideology. Ideologically he evolved from an Italian-style fascism (1931–1933) to a Dutch Nazism (1933–1940), then to a German-oriented Nazism (1940–1942) and finally to the most radical SS ideology, desiring one great Germanic empire in Europe (1942–1945). After the German defeat he returned to his ideas of the 1933-1940 period. ==Selected works==