Despite it being at the end of my series of questions, I'm actually most interested in how the system of international conferences, publications and reviews functioned during the period. I'll confess I'm not an expert in how it was done in the '30s and '40s compared to today, but obviously there were still research publications, symposiums, and other ways to confer with international colleagues about the work you're doing. Between German interference and restrictions on travel and publication, I'm wondering if a new style of academic work that relied less on international cooperation and review began to crop up at all, or if it was possible for academics in occupied France to work around their occupiers.
EDIT: Based on /u/itsallfolklore's insight below, I also have one more question now that the potential scale of academic liquidation has been made evident: what happened to the universities themselves in countries like Norway, France and Denmark? Did the majority still profess to be open in some way during the occupation, or did the degree of brain-drain from academic flight and German execution result in a situation where most universities were forced to shut their doors?
This is a small piece of the pie: in 1945, the US State Department asked Sven S. Liljeblad (1899-2000) to assess what remained of European anthropologists, folklorists and linguists in Europe, in the wake of the war. Liljeblad had risen in the pre-war ranks with his important 1927 dissertation on the Grateful Dead (a folklore motif). He had extensive contacts with continental scholars, and in the final years of the 1930s, he operated an underground out of Copenhagen to help Marxists, Jews, and others to escape the Nazis. With the outbreak of war, Liljeblad was forced to flee Europe since he was a "marked man." He had also stolen money for bribes (after the war, King Gustav VI Adolf wrote to Liljeblad to tell him all was forgiven and asking for his return to Sweden).
After corresponding and attempting to correspond with former colleagues, Sven sent a report in 1946 (and a follow-up report several months later) to State: he indicated that the vast majority of the pre-war European scholars outside of Germany, Britain, Ireland, Sweden, Spain, and Italy were dead. Scholars in occupied territories were some of the first victims of purges. In answer to your question in the case of this part of the academic community: the disruption was nearly total because it was usually fatal. Surviving scholars had often survived because they fled, leaving a disrupted, nearly non-existent network of scholars.
The source of this is correspondence in the Liljeblad papers at the University of Nevada, Reno Special Collections Library.
Edit: I meant to conclude with the following observation: based on the evidence in the Lijeblad Papers, it is easy to extrapolate that the US State Department reached out to other foreign scholars who had reached North America before or during the war, to ask them about survivors and the surviving networks in other academic fields. I imagine those records are somewhere in the State Department files or in the National Archive.