During the years 1967–1968 he was educated at the United States Army Command and General Staff College in Fort Leavenworth.

[11] Wahlgren led UNIFIL at the time when the Lebanese Civil War finally ended after fifteen long years with a peace agreement signed in the Saudi Arabian city of Ta'if in August 1990.

On Wednesday, 23 June 1993, however, Wahlgren's time in Yugoslavia ended after a game at a high political level where he was replaced by the French general Jean Cot.

[5] This was due to the fact that France in the United Nations demanded the leadership by virtue of having largest UN troop in the Balkans.

The general exchange was handled clumsily and caused some diplomatic complications between Sweden and the UN, which forgot to inform the Swedish government before the officialisation.

Wahlgren received an unreserved apology and praise from UN Secretary-General Boutros Boutros-Ghali for this and for his efforts in Yugoslavia.

[4][5] Wahlgren, who throughout his career carried with him a clear West Bothnian dialect, became one of Sweden's most internationally oriented officers.

He presented his visions of the possibilities of the United Nations in his publication FN:s insatser för fred mot år 2000 (1994).

[14][3] The banns of marriage were issued in February 1957[15] and the wedding was held on 1 March 1957 in St. Mary's Church [sv] in Helsingborg.