"Killing was not the original technique of the Final Solution, but it was the technique whose efficacy Himmler proved. [Peter] Longerich's magnificent biography of Himmler reveals him navigating among different policies of destruction, finding ways to match Hitler's immediate needs with German's practical possibilities. The grand 'positive solution' of a racially ennobling war gave way to the total 'negative solution' of the planned destruction of the people defined as the chief enemy, the Jews.
"Historians of Germany have pushed the date of the crucial decision to eliminate all Jews later and later, until it seems that it could go no further. They debate whether the critical moment was June 1941 (which few now believe), or October 1941, or December 1941. Longerich calmly pushes through late 1941 and January 1942, the month of the Wannsee Conference, without recording a moment from which the Holocaust as total extermination was inevitable. He believes that there was in fact no crucial moment when Hitler decided, or communicated his decision, to kill all Jews under German control. In his view, 'we should abandon the notion that it is historically meaningful to try to filter the wealth of available historical material and pick out a single decision' that led to the Holocaust. . . .
"It was only in the summer of 1942, Longerich maintains, that mass killing was finally understood as the realization of the Final Solution, rather than as an extensively violent preliminary to some later program of slave labor and deportation to the lands of a conquered USSR. To see mass killing as itself the Final Solution was, in Longerich's view, to abandon the prospect of any military victory over the USSR in the near future. . . .
"The emerging image of a Holocaust resulting from political motives denies Longerich's readers the expected moment of doom at the bottom of a descending narrative arc. More obstinately than almost all other historians, Longerich resists the temptation to insert a novelistic climax into the history of the extermination of the Jews."
So what were the decisive factors? 1) "the Führer and his ideology" as coupled with 2) "The political style of Hitler and other Nazi leaders", which "was to issue general guidelines and to expect subordinates to find the ways to realize them", to act "as creative conformists" in pragmatic response to 3) "Germany's practical possibilities" at any given point in an ever-shifting historical situation. "Hitler achieved his racist ends" by "requir[ing] of the Germans not just obedience but initiative," such that "the pattern of creative conformity established before 1939 enabled bloody escalation during the war."
Timothy Snyder, "A new approach to the Holocaust," The New York review of books 58, no. 11 (June 23, 2011): 54-56. Longerich's two books Holocaust: the Nazi persecution and murder of the Jews (Oxford: Oxford University Press, 2010 ), and Heinrich Himmler: Biographie (Berlin: Siedler, 2008), get the lion's share of the attention in this review.