Arnoldson, a man of humble origin, worked for the railways for 21 years. He eventually became an inspector. During these years, he read widely in history, religion and philosophy. He observed the political events of his day, especially the Danish-Austrian-Prussian War of 1864 and the Franco-Prussian War of 1870-1871. It was at that time that he developed his ideas on religion, politics and peace. He expressed them in his remarkable writings which he composed for the last 30 years of his life, including an essay on the history of international law (translated into English under the title of “Pax Mundi”), a contribution on religion in the light of research (1891) and the history of the pacifist idea (1901).

In his articles, novels and brochures, he addressed and advocated the concepts of liberalism and tolerance as well as freedom of thought and conscience, which he found in Unitarianism (one of the main movements of the Protestant Reformation) and the religious movements originating in the nineteenth century in Great Britain and New England.

He co-founded the Swedish Peace and Arbitration League, which was repeatedly nominated for the Nobel Peace Prize. He served as the League’s secretary. He edited pacifist periodicals and launched a campaign in support of arbitration in international relations.

He was involved in easing the tension between Sweden and Norway with regard to their union. Siding with Norway, which strove for the dissolution of the personal union between the two countries (dissolved peacefully in 1905), made him unpopular in Sweden. When he was awarded the Nobel Peace Prize, some of the Swedish newspapers were incensed.

Bajer was the son of a clergyman. He served in the Danish army, earning promotion to the rank of lieutenant. Between 1865 and 1872, he laid the foundations for his later career. He studied languages such as French, Swedish and Norwegian. At that time, he worked as a teacher, translator and journalist.

In 1872, he became member of parliament, retaining his seat for the next 23 years, independent of political affiliation. He advocated peace, the neutrality of Denmark, the Scandinavian unity, equal rights for women and reforms of the education system. He co-founded the Danish Women’s Society (1871) and established the Society of Nordic Free States. Soon he started to associate the idea of Scandinavian unity with neutrality and peace, becoming particularly interested in the activities of Frédéric Passy and the International Permanent League of Peace.

He became a leading figure of the peace movement. For 25 years, he served as secretary of the Danish Inter-Parliamentary Group, which he founded himself. He laid the foundations for the creation of the Scandinavian Inter-Parliamentary Union (1908). At the World Peace Congress in London in 1890, Bajer proposed the creation of a permanent bureau with headquarters in Bern. He became the first president of its governing board.