During the invasion of the Soviet Union and the Baltic states the Nazi process of killing Jews had been largely left to the mobile killing squads of the Einsatzgruppen. The pace and method of killing varied between the different Gruppen and had evolved over the course of the year. During the first phase only men and soviet officials had been killed by some units. Gradually women were included as a matter of course. On occasions only by default did the Nazi's discover that they didn't know what to do with the children left behind – so they began killing the children along with everyone else.
As the killings accelerated there appears to have been some competition to declare particular areas ‘Jew free’. During the course of late 1941 the overall attitude hardened into a belief that they had to kill every Jew. It would seem that there was no specific order or document, merely an interpretation of ‘what Hitler wanted’.
On the 16th December 1941 Hans Frank, the Nazi governor of what remained of Poland, now simply called ‘the General Government’ addressed his party colleagues on the ‘Jewish problem’. He made quite clear that the decision to embark on the mass murder of the whole population of European Jews had already been taken. There were to be further meetings to determine the logistics and the methods of killing:
I’ll be quite frank with you – an end has to be put to the Jews in one way or another. The Führer once said: if united Jewry again succeed in unleashing a world war then the result will not just be the bloodshed of the nations forced into a war by the Jews, but European Jewry will come to an end. […]
My attitude towards the Jews will therefore be based only on the expectation that they will disappear. They have to go. I have begun negotiations with a view to deporting them to the East. In January there will be a major meeting in Berlin on this matter, to which I will send State Secretary Dr Bühler. This meeting is to be held in the Reich Security Main Office and chaired by SS-Obergruppenführer Heydrich.
There will definitely be a major wave of Jewish migration. But what should happen to the Jews? Do you think that they will be housed in villages in the East? We were told in Berlin: why all the bother; we cannot do anything with them in the Eastern territories or in the Reich Commissariat liquidate them yourselves!
Gentlemen, I must ask you to rid yourselves of any feelings of pity. We must exterminate the Jews wherever we find them and wherever it is possible in order to preserve the overall structure of the Reich here. […] The Jews are extraordinarily malignant gluttons for us too.
It is estimated that we have 2.5 million Jews in the General Government [Generalgouvernement]; with those related to Jews by marriage and all that are associated with them perhaps now 3.5 million. We cannot shoot or poison these 3.5 million Jews, but we will be able to take action which will somehow lead to their successful extermination. This action will be connected with the major measures to be discussed by the Reich.