Birnbaum was born in Vienna into an Eastern European Jewish family with roots in Austrian Galicia and Hungary.

[3] His father, Menachem Mendel Birnbaum, a merchant, hailed from Ropshitz, Galicia (now Poland), and his mother, Miriam Birnbaum (née Seelenfreund), who was born in Carpathian Rus (now Ukraine), of a family with illustrious rabbinic lineage, had moved as a child to Tarnow, Galicia, where the two met and married.

He ran (in Buczacz, eastern Galicia) on behalf of the Jews (and with the support of the local Ukrainians) as candidate for the Austrian parliament.

Birnbaum, decrying political Zionism, 1919: And is it at all possible that we, who regard Judaism as our one and only treasure, should ever be able to compete with such expert demagogues and loud self-advertisers as they [the Zionists]?

His most well-known publication of this period of his life was Gottes Volk, "God's People" (1918, in German), translated in 1921 to Yiddish, in 1946 to English as "Confession" (slightly abridged), and in 1948 to Hebrew as "Am Hashem".

They fled together to Scheveningen in the Netherlands, with the help of businessman and diplomat Henri B. van Leeuwen (1888-1973) - Birnbaum, his wife, and their son Menachem, an artist, along with his own family.

There, Birnbaum, van Leeuwen, and banker Daniel Wolfe published the anti-Zionist newspaper Der Ruf ("The Call").