Foundations of Holocaust: The Final Solution, the Decision

“Don''t be misled into thinking you can fight a disease without killing the carrier, without destroying the bacillus,” (Hitler, 1920)
"Once I really am in power, my first and foremost task will be the annihilation of the Jews.”
(Hitler, 1922)
Background: Even as the United States, Britain, the Soviet Union and the Vatican were busy hustling prominent (Vatican) and/or ”useful” (America and her “allies”) Nazi war criminals out of harms way and safe from the Nuremberg trials, the International Military Tribunal was seeking answers as to how the Final Solution, the eradication of all Jews, everywhere, came to be German state policy even, at the end, its principal war aim? The answer appeared fairly clear at the time: Hitler had long proclaimed his intention; and Hitler was the undisputed leader of National Socialism and Germany. Yet despite his 1920 jail cell interview with the journalist Hell, his position in Mein Kampf and numerous public and private expressions of intent, for some the fact that no signed order by the fuehrer setting the Holocaust in motion represented a problem. Absent a Führerbefehl, a written order signed by Hitler, then some other explanation for the Holocaust must exist; that rather than following an intentional plan assigned from above, the extermination campaign was more the result of ground-up responses to immediate problems eventually coming together as a unified state project, “the Final Solution.” If this satisfied some scholars, it also served as rationale for Holocaust deniers: no written order, no Holocaust.” 
Although less intense today the controversy continues, promoting confusion, providing ammunition to those who would dismiss the Holocaust as a Jewish “invention;” consolation for Jews seeking assurance that the Shoah was, after all, just a one-time event. 
If, on the other hand, we accept the evidence of the systematic murder campaign as it exists, and that so systematic a national project is unlikely simply to have been decided and organized at that 1942 meeting at Wannsee, then it also seems clear that what preceded Wannsee was, if not a surviving “Hitler-order” or documentary blueprint, then certainly a long-understood within the Party hierarchy intention, as his speeches at party functions (1933, below) clearly demonstrate. 
The SS Einzatsgruppen were the first if imperfect because messy instrument, the bullet and trenches less efficient than Zyklon-B and cremation. Auschwitz, not the start, was just the final step in streamlining the Holocaust process: the industrialization of mass murder. 
The intention to murder each and every Jew within reach was understood by highest leadership to be state policy from Hitler’s 1932 electoral victory on: his intentions were a matter of pubic record at least since his earliest writings. Only the machinery of murder was still to be developed. If his writings reflect a graduated series of proposals, beginning with those apparently non-lethal such as emigration, extrusion and resettlement this reflects immediate political/technical expediency rather than ultimate intention.
Letter from Reinhard Heydrich to Martin Luther, Undersecretary at the Foreign Office, inviting him to the Wannsee Conference (Wikipedia)
The Wannsee Conference of January, 1942 is traditionally described as the start of the Holocaust. In fact Heydrich’s Einzatsgruppen had already been massacring Jewish communities for several years. So Wannsee’s principal task was not to establish but to expedite policy by a rational distribution of tasks and lines of communication between state agencies. 
It is one thing to intend a program of extermination, another to advertise it. So it is not surprising that a written order from the Fuehrer has not been discovered, that little on official state stationary exists as “blueprint” for the Holocaust. But Hitler was far less secretive the decade before leading his party to electoral victory in 1932. 
In his 1920 speech to the NSDAP:
“Don''t be misled into thinking you can fight a disease without killing the carrier, without destroying the bacillus… This Jewish contamination will not subside, this poisoning of the nation will not end, until the carrier himself, the Jew, has been banished from our midst.”
Mein Kampf, dictated while in a Munich jail, introduces “an asphyxiating gas” to murder Jews. And in his 1922 interview with the journalist Josef Hell he boasted, 
"Once I really am in power, my first and foremost task will be the annihilation of the Jews. As soon as I have the power to do so, I will have gallows built in rows - at the Marienplatz in Munich, for example - as many as traffic allows. Then the Jews will be hanged indiscriminately, and they will remain hanging until they stink; they will hang there as long as the principles of hygiene permit. As soon as they have been untied, the next batch will be strung up, and so on down the line, until the last Jew in Munich has been exterminated. Other cities will follow suit, precisely in this fashion, until all Germany has been completely cleansed of Jews."
When, ten years later, he actually became Führer and had the full machinery of the state at his disposal his speeches grow increasingly international in scope. In his 1933 speech to the NSDAP in Wilhelmshaven he already hints at a global Final Solution involving all willing or conquered Western countries:
“Only when this Jewish bacillus infecting the life of peoples has been removed can one hope to establish a co-operation amongst the nations which shall be built up on a lasting understanding.”
Hitler may or not have been the “mad man” his emotional speeches suggest; he was a magnetic orator. He understood that the technological means, domestic support and international acquiescence to his plans would take time to achieve. He was patient in preparing the ground. 
By 1935 the ground had been prepared to exclude German Jews from state and Volk. The Nuremburg Laws stripped German Jews of citizenship. And by 1938 the Party was confident enough to launch Krystallnacht, a two-day long pogrom that encompassed Germany, Austria and the Sudetenland. More than a hundred Jews were murdered; tens of thousands arrested and sent to concentration camps. 
Before and after the Krystallnacht pogrom German antisemitism was blatant. But between “antisemitism” and annihilation lies a wide psychological gulf. Hitler skillfully bridged that chasm by misdirection: he first proposed seemingly “humanitarian” solutions to the Jewish Problem among these emigration, then extrusion (forcing Jews across borders to neighboring states) and finally the creation of Jewish “reservations.” Two such projects were proposed,  in the French colony of Madagascar off Africa; and Nisko in the Polish Generalgouvernement border  separating German and Soviet Polish zones. Nisko was developed, to a point and, significantly, surrounded by slave labor camps. Auschwitz too hosted the AG Fargen slave labor camp, so the ultimate purpose of Nisko should be obvious since the purpose of slave labor was work to death. 
That such ruses and “programs” suggest that Germany’s planned final solution was not originally murderous, as many historians still cling to takes a leap, or outright denial of the facts. According to these the Final Solution only “reluctantly” turned to annihilation when German military success resulted in too many Jews to deal with while fighting the war! And so Germany turned to mass murder as “population control.” This basically is the Functionalist, the “crooked road” theory of the Holocaust. From what is written above functionalism, beyond Hitler’s purpose to buy time to develop greater efficiency in technology and bureaucratic management, to psychologically prepare Germany and the world, fails as explanation.
Whatever else, Hitler was a skilled politician. By allowing Jews to emigrate he forced the “democracies,” and particularly his loudest critic Franklin Roosevelt, to back up protest of German persecution by willingness to accept its victims. Hitler was, after all, just expanding on sterilization, endorsed by the US Supreme Court 1927 ruling explained by Justice Oliver Wendell Holmes:
“It is better for all the world, if instead of waiting to execute degenerate offspring for crime, or to let them starve for their imbecility, society can prevent those who are manifestly unfit from continuing their kind.”
So it came as no surprise that America also would fulfill his expectation by not accepting Germany’s Unfit, the Jews seeking refuge from German persecution. And that refusal would further legitimize Germany’s own antisemitic policies. 
As Hitler wrote admiringly in 1928 about the racist 1924 US Congressional Immigration Restriction Act: 
“That the American Union itself feels itself to be a Nordic German State… [is clear] from the manner in which it allots immigration quotas to European nations. Scandinavians… Englishmen, and finally Germans, are allotted the greatest contingents.” 
By forcing Roosevelt to publicly bar Jewish immigration Hitler trapped the president into demonstrating that little difference existed American and German antisemitism, a fact confirmed by polling of American attitudes at the time. 
Summary: There were several medial steps between 1933, when Hitler took office and made antisemitism state policy, and 1939 when the SS began its systematic murder campaign. Holocaust Deniers and many Holocaust historians, Jewish and not, point to “emigration,” “extrusion” and “Jewish reservations” as serious efforts by Germany to achieve a “non-lethal “solution to the Jewish Problem. I suggest these steps were in service of deception to buy time for Germany to prepare its public and the world; to develop the technology needed to carry through its real policy of mass murder. It may be unsatisfying that no written order by Hitler, that no documentary “blueprint” for the Final Solution exists. Still, this absence was consistent with Nazi awareness that their purpose was beyond easy understanding by “non-believers.” As Himmler said in Poznan, 
“It should be discussed amongst us, and yet, nevertheless, we will never speak about it in public.” 
But this does not yet explain why Hitler would risk losing control over those Jews that did manage to find refuge beyond Germany’s reach. Hitler was, if anything, supremely confident in himself and Germany to achieve his goals in the coming war:
Hitler did not want [did not plan for] a war with either Britain or the United States… [he] hoped that the United States, militarily unprepared and officially neutral, would not intervene before he won his, necessarily short, European war.”
In fact Hitler considered Britain and America natural allies of Germany, related by blood. He was apparently caught by surprise by Japan’s attack on Pearl Harbor which he felt obligated Germany to join its ally and declare war on the United States. He planned on a quick continental victory and, had he succeeded (something even Churchill and Roosevelt thought possible well into 1942), that even those few Jews who did manage to make it to the United States would, along with American Jewry, be returned to reach, and the Final Solution would almost certainly have been final. 
Recent writings in this Series: 

4. Foundations of Holocaust: a two-thousand year long Jewish Problem