In 1933, at the time of the Nazi rise to power, Birnbaum and his wife, together with their son Menachem (an artist) and family, who at that time were all living in Berlin, fled to Scheveningen, Netherlands, with the help of businessman and diplomat Henri B. van Leeuwen (1888-1973). There, Birnbaum, van Leeuwen, and banker Daniel Wolfe published the anti-Zionist newspaper "Der Ruf" ("The Call"). (Menachem and his family were murdered by the Nazis in 1944.) At the same time, their son Solomon (Professor of Yiddish and Hebrew paleography) and his family fled from Hamburg to England. Their other son, Uriel, an artist and poet, and his family fled from Vienna to the Netherlands in 1939. Van Leeuwen, also an Orthodox Jew, became a Dutch anti-Zionist leader and Bergen-Belsen survivor.