Nansen interrupted his research in 1905 to urge the independence of Norway from Sweden and, after the dissolution of the Union, served as his country's minister to Great Britain until May of 1908. In the next few years he led several oceanographic expeditions into polar regions, but once the world was plunged into war in 1914 and exploration was halted, he became increasingly interested in international political affairs.
For almost a year in 1917-1918, as the head of a Norwegian delegation in Washington, D. C., Nansen negotiated an agreement for a relaxation of the Allied blockade to permit shipments of essential food. In 1919, he became president of the Norwegian Union for the League of Nations and at the Peace Conference in Paris was an influential lobbyist for the adoption of the League Covenant and for recognition of the rights of small nations. From 1920 until his death he was a delegate to the League from Norway.
In the spring of 1920, the League of Nations asked Nansen to undertake the task of repatriating the prisoners of war, many of them held in Russia. Moving with his customary boldness and ingenuity, and despite restricted funds, Nansen repatriated 450,000 prisoners in the next year and a half.
In June, 1921, the Council of the League, spurred by the International Red Cross and other organizations, instituted its High Commission for Refugees and asked Nansen to administer it. For the stateless refugees under his care Nansen invented the "Nansen Passport", a document of identification which was eventually recognized by fifty-two governments. In the nine-year life of this Office, Nansen ministered to hundreds of thousands of refugees - Russian,Turkish, Armenian, Assyrian, Assyro-Chaldean - utilizing the methods that were to become classic: custodial care, repatriation, rehabilitation, resettlement, emigration, integration.
The Red Cross in 1921 asked Nansen to take on yet a third humanitarian task, that of directing relief for millions of Russians dying in the famine of 1921-1922. Help for Russia, then suspect in the eyes of most of the Western nations, was hard to muster, but Nansen pursued his task with awesome energy. In the end he gathered and distributed enough supplies to save a staggering number of people, the figures quoted ranging from 7,000,000 to 22,000,000.
In 1922 at the request of the Greek government and with the approval of the League of Nations, Nansen tried to solve the problem of the Greek refugees who poured into their native land from their homes in Asia Minor after the Greek army had been defeated by the Turks. Nansen arranged an exchange of about 1,250,000 Greeks living on Turkish soil for about 500,000 Turks living in Greece, with appropriate indemnification and provisions for giving them the opportunity for a new start in life.
Nansen's fifth great humanitarian effort, at the invitation of the League in 1925, was to save the remnants of the Armenian people from extinction. He drew up a political, industrial, and financial plan for creating a national home for the Armenians in Erivan that foreshadowed what the United Nations Technical Assistance Board and the International Bank of Development and Reconstruction have done in the post-World War II period. The League failed to implement the plan, but the Nansen International Office for Refugees later settled some 10,000 in Erivan and 40,000 in Syria and Lebanon.
Nansen died on May 13, 1930, and was buried on May 17, Norway's Independence Day.