Rubuta ci gaba don wannan sakin layi - A watan Mayu na 1940, Jamus ta Nazi ta mamaye Belgium. Bayan mika wuya na Belgium da farkon mamayar Jamus, shugaban POB<unk>BWP Henri de Man ya sanar da rushewar jam'iyyar gurguzu a matsayin wani ɓangare na manufar haɗin kai. Van Acker ya yi ritaya daga rayuwar jama'a. A cikin 1941, duk da haka, ya koma cikin jam'iyyar gurguzu ta haramtacciyar jam'iyya da kuma kungiyar kwadago ta karkashin kasa a karkashin "nom de guerre" "Monsieur André" kuma ya zagaya kasar yana tuntuɓar sassan jam'iyyar. Sa'ad da Aka 'Yantar da Belgium
a watan Satumbar 1944, Van Acker ya fito a matsayin shugaban jam'iyyar magajin POB<unk>BWP, Jam'iyyar Socialist ta Belgium ("Belgische Socialistische Partij", PSB-BSP).