Oh, they fought back. There were various instances of Jewish people fighting back but few of these attempts were successful. Most of them ended in tragedy.

There were several uprising in the Jewish Ghettos. The biggest was the Warsaw Ghetto Uprising which took place from April 1943 to May 1943. In June, there was the Częstochowa Ghetto Uprising. And a bit later in August, the Białystok Ghetto Uprising occurred. Even before the armed uprising, the Jewish people rebelled in unarmed ways against their German occupiers. There were secret meetings and discussions. Items such a religious artefacts and diaries were hidden so they could not be destroyed by the Nazis. When they forbad all newspapers except their own Nazi propaganda news paper, some Ghettos created their own underground newspapers.

There were also several uprising in the concentration camps. In August of 1943, there was an uprising in the Treblinka extermination camp. Arms and grenades were stolen from the Nazis and distributed to the prisoners. Sadly enough they were discovered before the distribution could be fully carried out and had to launch their attack prematurely. 1500 prisoners were killed; 70 escaped but were chased. Perhaps the biggest and most famous revolt in one of the concentration camps happened in Sobibor in October 1943. Here the inmates managed to kill several guards and about 300 of the 600 prisoners managed to escape. Only about 60 managed to survive that escape. There was also an uprising in Auschwitz in 1944 involving the Sonderkommandos (Jewish prisoners put to work on pain of death to work the gas chambers and ovens). They managed to destroy one of the crematoriums, but again, the uprising was ended.

In addition to all of this, of the Jews who managed to flee Nazi Germany, many of them joining resistance movements in the rest of Europe. I believe up to a quarter of the French resistance was Jewish. And then there is the amazing story of the The Bielski group. Founded by four brothers who fled into the woods after their parents and other family members were killed in the Ghetto, they fought the Nazis for two years through sabotage and guerrilla tactics. In addition to this, they managed to rescue and protect over one thousand Jews, many of who were women and children.