[1] Verhaegen was studying at the University of Ghent in August 1950, when he enlisted in the Belgian Volunteer Corps for Korea raised to participate in the Korean War.

Involved in nationalist politics, he served as chef de cabinet to Aloïs Kabangi, Minister of Economic Co-ordination and Planning, in the Lumumba Government.

[3] Verhaegen began researching political movements in the Congo in the aftermath of independence and formulated the idea of "immediate history" (histoire immédiate) which mixed anthropological, historical, and sociological approaches to current events on an extensive documentary basis.

[1] He wrote important studies on the Kwilu rebellion (1963–64), the nationalist leader Patrice Lumumba and the Alliance des Bakongo (ABAKO) political party.

A festschrift in Verhaegen's honour entitled Le Zaïre à l'épreuve de l'histoire immédiate was published in 1993, and included contributions by Immanuel Wallerstein and Catherine Coquery-Vidrovitch.

A note dated 12 September 1960 by the secretary of Belgian Minister without Portfolio Raymond Scheyven described the allocation of secret funds to several individuals, including Verhaegen.

"[5] Verhaegen explained that those funds were contributions for the creation of an International Centre for Cooperation and was labeled 'secret' since diplomatic relations between Belgium and the Congo were broken off.

Belgian academic Gauthier de Villers believed that "certain influential members of the group of experts or the Commission, too satisfied by being able to pinpoint in that way an engaged non-traditional and Marxist historian, were content with only doing a summary investigation.