[2] He was an open Scandinavist, and in 1864 he returned to Norway from a trip in Rome to agitate for Norwegian support of the Danish cause in the Second Schleswig War.
He even participated as a volunteer in the Battle of Dybbøl in April 1864, and after being demobilized from the war in August 1864, he walked back to Rome.
[3] Later, especially around 1866 and 1867, Bruun began supporting the use of the language form Landsmål (now Nynorsk), and was also inspired by N. F. S. Grundtvig and the Danish folk high school movement.
[3] Bruun's thoughts on education were chiseled out in the work Folkelige Grundtanker issued in 1878.He idealized Norwegian history, and wanted to replace Greek and Latin languages with the Old Norse Edda in schools.
At the same time as hailing the Norwegian farmer, he was clear that the farming populace would need to be educated, especially over the next "century", hence the folk high schools.
In 1905 he chose not to support the radical constitutional policies that led to the dissolution of the union between Norway and Sweden.
Bruun retired as vicar in 1918, and retreated to Østre Gausdal where he died on his farm in July 1920.