In the early 1940, March began the preparatory works, as he also planned the partial remodeling of the fortress outside of the sports complex, too. He incited archaeological survey and invited German architectural historian Daniel Krencker to study the excavations. Within the scopes of the Nazi expansion of the megaprojects, and augmentation of the German historic role and importance in this region, Krencker praised March's project as the "artistic dream, which represents rare and major German cultural act which will contribute to the old German glory of Belgrade". Just few days after German scientists left the fortress, Germany attacked Yugoslavia on 6 April 1941. Olympic complex was pushed aside, shifting the focus of the Germans to the archaeological exploration of the fortress during the war.