As head of the War History Department, he led the work on "Sveriges krig 1611–1632" ("Sweden's war 1611–1632"), a book in eight volumes published 1936–1939. He himself conducted war history archive research in Latvia and Estonia in 1922, in Germany, Danzig and Copenhagen in 1923, in Finland in 1925 and 1926 as well as archival research and battlefield surveys in Danzig, Poland and Germany in 1927. He led archival research and battlefield research in Belgium, Netherlands, Czechoslovakia, Germany and Austria in 1929 and in several other countries in 1930.