In July 1941, the German occupation authorities became suspicious of the MNR and it was forced into hiding.[1] After the arrest of Mertens de Wilmars in May 1942, it became overtly anti-German and began to engage in resistance activities.[2] The group produced underground newspapers (including the Dutch language newspaper Vrije Volk) and collected military intelligence. The MNR also provided help to Jews hiding from German persecution, Allied pilots shot down in occupied Europe and Belgian workers avoiding labour service in Germany.[1]
In collaboration with the Secret Army and the Witte Brigade, the MNR participated in the capture of the Port of Antwerp shortly before the Allied liberation in September 1944.[2] The operation prevented the Germans from destroying the installations and provided the Allies with access to their first intact deep-sea port.
160 members of the MNR were executed or died in Nazi camps. Around 100 were killed in action during the liberation of the Port of Antwerp in September 1944.[2] A monument to five members of the group killed during the liberation of Brussels is visible next to the Royal Museums of Fine Arts.[3]
Dujardin, Vincent; Van den Wijngaert, Mark (2010). La Belgique sans Roi, 1940–1950. Nouvelle Histoire de Belgique. Brussels: Le Cri édition. ISBN978-2-8710-6520-3.