Black Earth: The Holocaust as History and Warning. By Timothy Snyder.Tim Duggan Books; 462 pages; $30. Bodley Head; £25.

“A HISTORY of the Holocaust must be contemporary,” writes Timothy Snyder in the prologue to “Black Earth”, an impressive reassessment of the Holocaust, which steers an assured course between two historical traps. It is a mistake to see the Nazi genocide as an event too unique to be rooted in the past or to have relevance to the present. Yet it is also wrong to flatten the singularity of the deliberate mass murder of Europe’s Jews into a general warning against racism or xenophobia.

Mr Snyder, a professor of history at Yale University who specialises in central and eastern Europe, begins by showing the Darwinian, deterministic thinking behind Adolf Hitler’s ideal world. Superior races (Germans, British and Americans) were in a ruthless contest with lesser races for territory and natural resources. Even to consider a world in which human beings could live harmoniously side by side was in the words of “Mein Kampf”, “un-nature”.

In Hitler’s universe the Jews were an alien “counter-race”, whose unnatural beliefs included dangerous and subversive politics. For the good of the planet, therefore, Jews must be removed from the face of the Earth, though it would have been little comfort to the murdered millions to know that they were being shot and gassed for ecological, rather than racial reasons. Another of Mr Snyder’s insights is that the Holocaust intensified as military success became more distant: having failed to vanquish the Soviet Union, the Nazis took extermination as a consolation prize.

One of the most controversial arguments in Mr Snyder’s book is the contention that absence of state structures, and the lack of legal status that ensued, aided the executioners. Jews were most vulnerable in places where citizenship, identity, protection, the right to property and ultimately life were no longer guaranteed by any kind of legal and bureaucratic structure. In France and Italy, where national governments continued more-or-less to function under occupation, three-quarters of the Jews survived. In eastern territories, which suffered “double occupation”, first by the Soviets under the Molotov-Ribbentrop pact and then by the Nazis, at least 90% of them perished.

“Black Earth” will prove uncomfortable reading for many who hew to cherished but mythical elements of Holocaust history. It highlights how Stalinist policies paved the way for Nazi extermination. After the war, the Soviets often portrayed Jews as “victims of fascism”, glossing over how communist cadres had often been the first collaborators, proving their loyalties to their new masters by murdering Jews. Mr Snyder also argues convincingly against the left-wing view that the Holocaust stemmed from imperialism, or the failures of bourgeois capitalism.

The weakest parts of Mr Snyder’s book are the environmental and political prescriptions. Global warming does not have much to do with Hitler’s dementedly brutal ecological thinking. Comparisons between Nazi propaganda and the current vogue for conspiracy theories in Muslim countries, that hold Israel responsible for most of the wrongs in the Middle East, are not conclusive. Paranoia and myth-making long predate Hitler.

Thinking about the Holocaust should not be easy. Mr Snyder’s flawed but powerful book challenges readers to reassess what they think they know and believe: a worthy memorial to the victims.