Everyone, during the German occupation of Poland, had to have a kennkarte, or identity document. These came in four categories and colors. Germans who had been born in Germany, the so-called Reichsdeutschen, were entitled to one kennkarte, individual who could prove third generation German ancestry and declared themselves to be German, the so-called Volksdeutschen, got another. The non-Germans who could prove the absence of Jewish ancestry were termed Nichtdeutschen and got a different kennkarte from those in the last category, the Juden, who, regardless of their faith, were of Jewish or partly Jewish ancestry. Possessors of this latter kennenkarte were obliged to wear a yellow armband hearing a Star of David design. What kennkarte one possessed determined not only what curfew hours applied to one, where one could live etc. but also the amount of food coupons one was entitled to. Printed with the same complexity of design as banknotes, the kennkarte was difficult to forge.

In the Fall of 1940, Warsaw holders of the Juden kennkarte were ordered to move to the "Jewish Residential District", or Ghetto, which the Germans carved out of the city. Other areas of town were reserved for the Germans, previous owners of properties in such areas being simply expropriated. The remainder of the town was where the Nichtdeutschen were to live. This, the Germans termed the Aryan areas.

Though at first Jews could leave the Ghetto temporarily, this was soon forbidden and any Jew found on the Aryan side of the wall, unless possessing a special pass, was subject to summary execution. Yet, however dangerous it was for Jews to try to leave the Ghetto, in the long term their chances of survival were much greater on the Aryan side.

Survival on the Aryan side required assuming a different identity, securing an Aryan (i.e. Nichtdeutschen) kennkarte to match that identity, shelter, (i.e.: the willingness of an non-Jew, or more likely, a non-Jewish family, to provide accommodation), and credible employment, since non-Germans who were not working were subject to deportation for forced labor to Germany.

The Germans were not easily fooled. If suspicious, they would check out the details of an assumed Aryan identity, checking birth records, school records, etc. To pass muster, the identity had to be that of a real person who was, for some reason, no longer around, and the details of the identity had to be carefully learned and rehearsed. Acquiring new identity and an Aryan kennkarte to go with it required the help on non-Jews as did meeting the other requirements for survival. That in turn was rendered all the more difficult by the fact that the Germans decreed that any non-Jewish individual or family found to sheltering, transporting, or providing food to a Jew was also subject to immediate execution. Of all the countries that the Germans occupied during the WWII, Poland was the only one where the Germans issued and implemented this draconian decree.

For some, passing for an Aryan was made harder, as many accounts from that time testify, by facial features that were sufficiently outside the range of those of the city's ethnically Polish population to raise questions about their ancestry. Likewise, for those who spoke Polish with an accent as distinctive as the Brooklyn one is in the US, or spoke it poorly, their first language having been Yiddish, assuming an Aryan identity presented problems. Finally, in the case of males, the Germans could ultimately check whether the person in front of them had been circumsized, a practice universal among Jews but not then practiced by Christians.

A further impediment to the survival of the Jews in Warsaw was simply the vast scale of the problem. In the Ghetto, the Germans crowded 550,000 Jews. The population on the Aryan side was 700,000.

Figures regarding how many Jews in Warsaw, by virtue of being on the Aryan side, were able to survive the liquidation of the Ghetto are not easy to ascertain. However, Marek Edelman, the surviving leader of the Ghetto Uprising stated in a 1993 interview published in the Polish weekly, Tygodnik Powszechny, that "Twelve thousand Jews survived in Warsaw until the Warsaw Uprising [i.e. the 1944 Uprising after which the Germans forced the entire population of Warsaw to leave the city]."  "In order for 12, 000 Jews to survive"- Edelman continued, "100,000 persons had to had to be involved."

Edelman's estimates that given the complexity of the task, eight Poles was needed to be involved in different aspect of the effort in helping one Jew survive. There were among the Poles, informers. And others who were oblivious and did not care. But also there were many who did care and a great risk, did what they could to help.

In Jerusalem, at Yad Vashem , individuals who risked their lives to save the lives of Jews during the Holocaust, and whose actions in this regard can be verified, are honored by having their names permanently engraved on the Honor Wall in the Garden of the Righteous. Of the 18,262 such names, 5503, or 30%, are those of Poles, the largest group from any nation.

To render the circumstances described above more tangible two sets of events are recounted as they affected individuals. Exit from the Ghetto is a chronicle of how two families crossed to the Aryan side soon after the start of the massive deportations to Treblinka's gas chambers in July 1942. Sheltering on the Aryan Side describes how a family, later honored at Yad Vashem for their action, provided refuge for a couple of Jewish girls.