An idle comment, one might think. Historians like to point out the Nazi dictator's inconsistencies and hesitations over small matters. The German dictator sometimes could not make up his mind about timing his moves, and he liked to set his lieutenants against one another, growing bored with their assigned tasks and impatient with the preparatory work that was necessary to achieve his grand designs. Set on dominating the European continent from the Atlantic to the gateways to Asia, he had no blueprint for how to proceed, and no systematic idea of how to organize and run the empire that would lie at his feet.

But say what one will about Hitler, when it came to the big picture, he was ruthlessly consistent and unfailingly determined. While he had contempt for the Western Europeans, especially the French, and even his allies the Italians, he despised the Slavic peoples, whom he sometimes lumped together and sometimes disaggregated into nationalities for which he harboured special grudges and hatreds. Hitler was the heir of 19th-century German nationalism's commitment to Lebensraum, or living space in the East - not an original aim, but one to which he remained rigidly committed through thick and thin, and with a deep personal obsession.

Mark Mazower's large and impressive book about Hitler's empire reminds us that his was an imperial project, supposed to last for a thousand years, making the Führer among the last European empire-builders - a role in which we are not perhaps accustomed to seeing him. Hitler and his entourage were especially influenced by the British Empire, and there were times when he hoped they could be persuaded to go along with his goals. With their great maritime power, the British could dominate Asia and Africa; but thanks to the prowess of the Wehrmacht, a land army unmatched in the world, he thought, Germany's historic empire was in the east of Europe. To his ambassador to France, Hitler mused in 1941 that Russia, as far as the Urals, would become "our India." And his occupation forces got the message. "We are here in the midst of negroes," said one German official in the Ukraine in 1942.

The Nazis' obsessive belief in 'Germanic blood' sent them into paroxysms of destruction and eventually self-annihilation

Formidable as the Hitlerian empire seemed at its height in 1942, when Continental Europe was in its iron grip and even the Soviet Union seemed to be on the verge of collapse, the contradictions and weaknesses of the German domination were glaringly evident - constituting the principal theme of Mazower's magisterial work. At the core of the entire, vast enterprise was an absurd ideology of race. "Our mission is not to Germanize the East in the old sense - bringing the German language and laws to those living there," wrote SS chief Heinrich Himmler, "but rather to ensure that in the East dwell only men with truly German, Germanic blood."

In truth, of course, there was no such thing and the mission was impossible. The Nazis' obsessive belief in "Germanic blood" sent them into paroxysms of destruction and eventually self-annihilation. From the start, the Nazis feared and loathed the Jews, whom they insanely believed to be their greatest global threat. Hence they set upon a policy of persecution and eradication - eventually escalating to a European-wide policy of mass slaughter. As for the Slavs - Poles, Belorussians, Ukrainians, Russians and the Baltic peoples - they too were despised and victimized, ground down, enslaved, exploited, brutalized and uprooted.

What the Nazis failed to appreciate was how these policies sapped the sinews of empire and fatally weakened their grip on the territories they occupied. Chronically short of labour, and with their manpower fed into the meat grinder of the Eastern Front, the Germans never figured out how to harness the working populations of their conquered territories. Almost invariably, the Germans' racial fantasies and instinctive brutality undermined the productive capacity of the millions of foreigners who toiled for the Third Reich. In occupation, where there were often willing collaborators and subject nationalities eager to be liberated, the Germans preferred domination, repression, robbery and murder to policies that might have enticed the subject people to assist their conquerors.

Hitler's empire, we are reminded by Mazower's broad thematic survey, was not only without a credible, unifying ideology - other than implacable German domination and racial superiority - it was also without a plan, a clear guide to how it would be ruled and organized. Driven by racial fantasies of wrapping all Germans within the imperial fold, the Nazis set about to move vast numbers of people about the continent. Hundreds of thousands of Jews and Slavs would be uprooted, expunged from territories on the frontiers of the expanded German empire and sent eastward. And hundreds of thousands of ethnic Germans, the so-called Volksdeutsche, were to be gathered from wherever they lived - the Baltic states, Poland and the occupied Soviet territories, and brought "home" to Germany.

On paper, this was to be the largest, the most ambitious population movement in history. In practice, it was a shambles. Moving huge numbers of peasants was beyond the capacity of even the Germans in wartime, not to mention counterproductive economically. There were never enough Germans to resettle within the Reich, many did not want to do so, and even when they were brought westward, they could not be settled productively anywhere. The whole misbegotten effort proceeded in fits and starts, was accompanied by great brutality and wasteful destruction, never met its targets and served only to undermine the productive food-producing capacity so badly needed by the embattled German state.

Increasingly desperate in 1943, the managers of this empire quarrelled among themselves, worked within bureaucracies pitted against bureaucracies, divided into pragmatists and ideologues, and degenerated into harsh brutality and genocidal repression.

There were places that escaped the worst. Mazower has a few pages on France, reminding us that life could be easy for some, for a time, and that German occupation policy might mesh with local account-settling and political ambition.

But for much of the continent, especially as things got worse in the last years of the war, life under the Nazis was a dark age, in which the Germans squandered any prospect of a stable colonial system. This is a sombre, clear-eyed, imaginative book about one of the greatest destructive projects the world has ever known.

Michael R. Marrus is a senior fellow of Massey College. His next book is Some Measure of Justice: The American Holocaust-Era Restitution Campaign of the 1990s.