During the liquidation itself, the Youth Movements met and formed the Jewish Fighting Organization, known by its Polish initials, Z.O.B. . Those present were Hashomer Hatzair, Dror Hechalutz and Akiva. By November, the other left and centre Zionist Youth Movements had also joined, as well as the Bund and the Communists. The leader was the Hashomer Hatzair madrich, Mordechai Anielewicz.

Betar established their own group, called the Revisionist Jewish Military Union, known as the Z.Z.W.. While we do not know exactly when it was formed, it played a major role in the Resistance.

Ghetto Survivors are divided as to why the groups could not unite before so terrible an enemy.

• Z.Z.W. survivors claimed it was because they were not permitted to join as Betar, but only as individuals.
• Z.O.B. members claim it was because Betar wanted to lead the resistance, refused to hand over their weapons and propagandized against the Z.O.B. in the Ghetto.

In the end, in April 1943, the two groups did unite under Anielewicz's command.