When World War II broke out in 1939, Bergmann sought to join the South African army, but as he felt his name was too German-sounding (there was significant anti-German feeling as the war loomed, and as the Nazi persecution of the Jews and the Holocaust had not yet happened, this feeling made no distinction between Germans and German Jews), he removed the second "n" from his name, adopting the Dutch variation of the surname.

After the war, Bergman earned a living from what were ostensibly his hobbies, namely ice skating and photography.

Several of his pupils became prominent South African photographers, and he taught ice skating at the Empire Exhibition.

It was during his military service – especially during his time in Italy and Palestine – that Bergman became interested in numismatics, a subject for which he would gain ultimate renown.

He served as Secretary and later President of the South African Numismatic Society, an organization in which he was to remain active all his life.