Conflictual relations between language groups make Belgium a fruitful ground to study the interplay between historical knowledge, importance, collective memory and social identity related to historical events. This study compared German-speaking and French-speaking Belgians on the these dimensions for a historical event for which contrasted responses were expected, the centenary of Armistice on 11 November 2018. We also focused on generational differences by comparing senior, intermediate, and junior age cohorts. Results showed no generational differences but revealed that German-speakers construct their social identity differently than French-speakers. Namely, German-speaking Belgians integrated political with non-political events in their collective memory and relied more on school as source of knowledge and nationally relevant memories. In contrast, French-speaking Belgians relied on family and friends as source of knowledge, intertwined more personally and nationally relevant memories, and showed a strong association of national identity with the importance attributed to World War I.