Fareynikte Partizaner Organizatsye
The Fareynikte Partizaner Organizatsye (Yiddish: פֿאַראײניקטע פּאַרטיזאַנער אָרגאַניזאַציע; "United Partisan Organization"; referred to as FPO by its Yiddish initials) was a Jewish resistance organization based in the Vilna Ghetto in German-occupied Lithuania and founded on January 21, 1942. The clandestine organisation was established by Communists as well as left- and right-wing Zionists.
Source: Wikipedia — Fareynikte Partizaner Organizatsye (CC BY-SA 4.0)