an essay by Gord McFee
One of the most interesting, and hotly debated, aspects of the Holocaust is when Hitler ordered it to begin.
The thinking to now has been that the decision was made in early to mid 1941, and that it got into full gear in early 1942. That thinking is now challenged by the recent discovery of hitherto unavailable documents, recently uncovered by German historian Christian Gerlach.  The new documents include a diary entry by Propaganda Minister Joseph Goebbels of December 12, 1941 and a portion of Reichsführer-SS Heinrich Himmler's diary entry of December 18, 1941.
Before getting to these recent discoveries and what they mean, it is in order to briefly recapitulate the current state of thinking on the matter. It is generally accepted that the decision was made to physically exterminate the Jews in early to mid 1941.  Hitler's secretary remembers a private meeting between Himmler and Hitler in the early spring of 1941, after which Himmler sat at her desk with a very troubled look on his face, put his head in his hands and said: "My God, my God, what I am expected to do".  She is convinced that that was the day Hitler ordered him to murder the Jews. Other accounts suppose that the decision was made roughly around the time between March 1941 and the invasion of the Soviet Union. (Research in this area is hampered by the fact that no written Hitler-Order launching the Final Solution has ever been found, and that if there ever was one, it most likely was destroyed.) Rudolf Hoess, commandant of Auschwitz  and Adolf Eichmann, head of Amt IVB4 (Jewish Affairs)  both speak of having been told of a Hitler-Order in early summer of 1941.
Historians have generally thought that the Final Solution unfolded like this. First, the Einsatzgruppen (special task forces) entered the Soviet Union behind the invading armed forces in late June 1941 and began shooting Jews where they were found. Roughly 500,000 Jews were killed in this way between July and December 1941. At that time, the sheer number of Jews to be killed and the effect on the police of shooting women and children caused other methods to be investigated, culminating in the establishment of death camps such as Auschwitz, Treblinka and Sobibor in early 1942, to which Jews were transported and gassed with carbon monoxide or prussic acid (Zyklon B).
This raises several questions, such as:
The recent discoveries allude to a clear and unambiguous order from Hitler himself to kill the Jews. At the same time, they suggest three revisions to the current theory may be in order. First, it is now undeniable that Hitler personally ordered the overall Final Solution decision; second, the decision was not made prior to the invasion of the Soviet Union - rather, the ultimate decision was taken near the end of 1941; third, the Final Solution was not a smoothly evolving process, but rather more dependant on the vagaries of the war effort.
The Recently Discovered Documents
The two recent discoveries are:
Bezüglich der Judenfrage ist der Führer entschlossen, reinen Tisch zu machen. Er hat den Juden prophezeit, daß, wenn sie noch einmal einen Weltkrieg herbeiführen würden, sie dabei ihre Vernichtung erleben würden. Das ist keine Phrase gewesen. Der Weltkrieg ist da, die Vernichtung des Judentums muß die notwendige Folge sein.
With respect of the Jewish Question, the Führer has decided to make a clean sweep. He prophesied to the Jews that if they again brought about a world war, they would live to see their annihilation in it. That wasn't just a catch-word. The world war is here, and the annihilation of the Jews must be the necessary consequence. 
Judenfrage / als Partisanen auszurotten
Jewish Question / to be exterminated like the partisans
Hitler Personally Ordered The Final Solution
Most experts have agreed that an action on the magnitude of a mass genocide, with the resultant possible ramifications, could not have proceeded without Hitler's personal approval. Until now, no written decision from Hitler has been found, although there are compelling indications that a verbal decision was certainly given.  The recent discoveries cannot be called a written decision (which, if it ever existed, was almost certainly destroyed by the end of the war), but they are certainly unequivocal confirmation that a clear decision was taken by Hitler. Even better, they help pinpoint the time it was taken.
The Decision Was Made At The End Of 1941
The new evidence strongly suggests that Hitler decided once and for all, in early December 1941, to exterminate all of European Jewry. That squares with the words, "aspired final solution" in Goering's order to Heydrich of July 1941, and helps to explain why the Wannsee Conference took place so long after the Goering order had been issued, that is, the final order had still not been given in July 1941.
This does not mean that no order at all had been given at the time of the invasion of the Soviet Union. Indeed, it is certain that an order to kill Jews, commissars and other "undesirables" had been given before the Soviet invasion, and it may well be that order that Hitler's secretary refers to. It most likely took the form of Hitler telling Himmler that as part of the invasion, the individuals mentioned above would be systematically killed and that Himmler was charged with execution of the order. And it is most likely this order that Eichmann, Hoess and others referred to in their various testimonies.
But in addition to that, these individuals would have been aware of Goering's order for the administrative work to be done towards an "aspired" final solution. Everyone knew that a final solution - a decision to annihilate all of European Jewry - could only be made by Hitler. And Hitler was legendary for hesitating, at times with almost disastrous effects, when faced with grave decisions, such as the Roehm Purge, the Munich Crisis and whether to run in the presidential election of 1932.  It would be entirely in keeping with Hitler's personality if he hesitated several months after ordering the Einsatzgruppen shootings - a kind of pre-final solution - before he could bring himself to make the ultimate decision. Goering's order notwithstanding, there was little concrete action that Heydrich could take until there was a definitive decision from the man at the top. And the man at the top did not decide until December 1941.
One can only speculate what finally catalysed Hitler into making the ultimate decision in December 1941, but a look at the situation at that time suggests several factors played a role. First, with the Japanese attack on Pearl Harbor, the American declaration of war to Japan, and Hitler's own declaration of war against the United States, Hitler now had the "world" war referred to by Goebbels in his diary entry of December 12, 1941. Second, the first great reversal of German fortunes in the war against the Soviet Union had taken place. On December 5, at the very gates of Moscow, the German army was stopped its tracks by the onset of a vicious Russian winter. Temperatures dropped to 31 degrees below zero that day, and the next day to 36 below. The Germans were not equipped with winter gear, the panzers broke down, and, on the 6th, General Georgi Zhukov attacked on 200-mile front before Moscow with 100 divisions that the Germans had not even known existed.  Hitler must have known at this stage that his war effort was in serious, perhaps grave danger. Third, the sheer numbers of Jews to be killed and the difficulties doing it caused for the police who did the shooting were passed on by Himmler to Hitler. There had been discussions on the use of poisonous gas as a means of killing Jews and avoiding public spectacles that sometimes accompanied shooting throughout the autumn of 1941. 
Against this backdrop, it can be plausibly argued that December 1941 was a kind of watershed for Hitler. The congruence of events may well have forced him into a position where he burned his bridges.
Complementing the task already assigned to you in the directive of January 24, 1939, to undertake, by emigration or evacuation, a solution to the Jewish question as advantageous as possible under the conditions at the time, I hereby charge you with making all necessary organizational, functional, and material preparations for a complete solution of the Jewish question in the German sphere of influence in Europe.
Insofar as the jurisdiction of other central agencies may be touched thereby, they are to be involved.
I charge you furthermore with submitting to me in the near future an overall plan of the organizational, functional, and material measures to be taken in preparing for the implementation of the aspired final solution of the Jewish question.
Gordon McFee received his Master's degree in 1973, from the University of New Brunswick, Canada, and Albert Ludwigs Universität, Freiburg im Breisgau, Germany (split studies), in history and German.
[Editor's note: for a slightly different point of view on the evolution of Hitler's mindset, see the work of Dr. Stig Hornshøj-Møller on the Nazi propaganda film Der ewige Jude ("The Eternal Jew"). In the view of Hornshøj-Møller, this film - produced with Hitler's close supervision in mid-1940 - reveals an effort to lay the groundwork for the coming Holocaust.]