The lawyer Hubert Pierlot joined the Catholic Party in the 1920’s. As senator for the Belgian Province of Luxembourg, he occupied important ministerial posts during the interbellum years. In February 1939 he became Prime Minister. In May 1940, Pierlot came in conflict with King Leopold III, who, without the consent of his ministers, decided to capitulate and stay in Belgium as prisoner of war. Pierlot chose otherwise. In September 1940 he fled to London, where he formed, with Ministers Paul-Henri Spaak, Camille Gutt and Albert de Vleeschauwer, the core of the Belgian government in exile for four years. During these years he was Prime Minister and Minister of Defence and in that capacity he played an important role in the war time negotiations between the Allies. His government set up the 1st Belgian Infantry Brigade or so called Piron Brigade (Brigade Piron), that would play an important role in the liberation of Belgium and the Netherlands.
On 8 September 1944 Pierlot returned to Brussels, where he headed a government of national unity. This government was weakened by all the problems Belgium faced during the next winter, such as food supply problems, the fierce fighting during the German Ardennes Offensive (Battle of the Bulge) and Pierlot’s growing impopularity in royal circles because of his disagreement with King Leopold III during the war. His government fell in February 1945. Pierlot returned to his position as Senator. But in 1946, disappointed and abandoned by his own party in the Royal Question, he retired from politics.