From 1938 to 1946 he was a programme secretary in the Norwegian Broadcasting Corporation (NRK). When Norway was invaded by Germany in April 1940, Rytter fled the country together with the Norwegian royal family and cabinet. After a short period in Stockholm he reunited with the Norwegian authorities-in-exile in London, where he worked for the NRK and BBC until 1944. He received basic military training, in Scotland. He has also been credited with suggesting Martin Linge as an SOE agent in the fall of 1940. In 1944 Rytter travelled to Finnmark to oversee the liberation of Northern Norway as an officer of information. Norway was fully liberated on 8 May 1945.