The Triumph of the Dark: European International History 1933-1939, By Zara Steiner

This book may not be the last word about international relations during the 1930s but it is perhaps the last half-million words. Debates over specific developments leading up to the Second World War will continue, but it is unlikely that such a vast and authoritative synthesis will ever again be produced. The second volume of Zara Steiner's study of European diplomacy between the wars is substantially longer than its predecessor, The Lights that Failed, and even specialists will be awed by its erudition. They will, especially, look on her bibliographies and despair. Furthermore, the book is important for cutting through thickets of revisionism and setting the record straight about the folly of appeasement and the guilt of Hitler – AJP Taylor's day-dreaming Führer, who accidentally stumbled into war, is consigned to the dustbin of history.

The dictators are the clear villains of the story. Hitler was pragmatic as far as tactics went, exploiting situations with diabolical skill. But he never lost sight of his strategic goals: the struggle to win Lebensraum in the east, the eradication of the Jews, the establishment of an Aryan world order. As Steiner says, "Hitler was an opportunist who knew where he was going."

Mussolini was a Fascist who did not know where he was going. Steiner exposes the hollowness of his pretensions, rightly reacting against recent attempts (notably by Renzo de Felice) to rehabilitate the Duce. Far from recreating the Roman empire by invading Ethiopia and supporting Franco in the Spanish Civil War, he weakened the least of the great powers. Italy's impotence was exposed in 1939 when, despite the Pact of Steel with Hitler, Mussolini was forced to declare "non-belligerence" – his bombastic euphemism for neutrality.

Stalin created a new form of tyranny. He probably killed more than a million of his own people during the Great Terror of 1937-8 and, as Steiner writes, "the purges were rooted in Stalin's fierce determination to establish his control over all men and institutions that might threaten his monopoly of power". His conduct of foreign affairs was equally malign. The Red Tsar was so suspicious of the imperialist powers that he finally put his trust in the Führer, signing their infamous compact in August 1939 and participating in the dismemberment of Poland. Impervious to evidence that the Teutonic crocodile was proposing to eat him last, Stalin promised to help Hitler in the European war: "The USSR is interested in a strong Germany and will not let it be beaten."

However, Steiner is also justifiably critical of the democratic leaders. She pays tribute to Roosevelt's political adroitness but shows how slippery he was as an ally. French politicians, fearful about of their country's vulnerability, were much worse. A British ambassador remarked that "the only white thing about Laval was his tie" – and that was seldom sent to the laundry. Foreign Minister Bonnet was hopelessly defeatist and congenitally dishonest – it was said that he lied like a tooth-puller. And Daladier, the prime-ministerial "Bull of the Vaucluse", notoriously had the horns of a snail; when he banged the table it was a sign that he was about to capitulate.

At home, Anthony Eden was wobbly and disingenuous, earning his reputation as an anti-appeaser only by resigning in a fit of pique. Lord Halifax was aloof and his celebrated moral sense was largely in abeyance – he regarded the Führer as outlandish rather than evil. Neville Chamberlain's failures were legion and Steiner is scathing about his overweening vanity and misplaced self-confidence. Of course, his anxiety to avoid war was admirable. But he completely failed to understand Hitler, assuming that he was amenable to personal persuasion and judicious concession. About the only joke in the book is the Foreign Office's animadversion on the PM's achievement at Munich: "If at first you can't concede, fly, fly, fly again."

The Triumph of the Dark is austerely academic. It concentrates on documentary minutiae at the expense of the human dimension. There are few telling anecdotes, colourful vignettes or vivid character sketches. Steiner explicates the Nazi-Soviet Pact, but does not mention Ribbentrop's inventive eulogy to German-Russian friendship which Stalin deleted as unbelievable, since for years "we have been pouring buckets of shit over each other's heads."

At times her writing is uneven and the narrative is lost in the detail. Indeed, there are occasional repetitions and some overlaps with the previous volume, and the whole would have benefited from pruning. Yet despite the quibbles and against the odds, the book is a terrifically good read.

It is, after all, a definitive account, the distillation of a lifetime's dedicated scholarship. Steiner has marvellously lucid chapters on events such as the Spanish Civil War, Mussolini's Abyssinian adventure and Japan's developing aggression in the Far East. She shines new light on Poland, the Balkans and the Soviet Union. She is particularly illuminating about economic conditions and their impact in the wake of the Depression. And she musters an impressive array of facts and figures about rearmament. Thus she maintains convincingly that Britain did not divert resources from home defence in order to protect the Empire, that the Royal Navy could and should have bottled Mussolini up in the Mediterranean to stop his rape of Ethiopia, and that the democracies were in a relatively stronger position to fight Germany in 1938 than in 1939. No short review can do justice to the book's riches.

Surprisingly, though, much about the devil's decade remains obscure. As Steiner acknowledges, Roosevelt's motivation is baffling. Stalin is a partial enigma, at least until the Russian archives are fully open, and it is impossible to say whether he would have intervened in 1938 if the democracies had fought for Czechoslovakia. The Vatican is as secretive as the Kremlin. Japanese policy-making defies clear explanation. Above all, there is the question posed in Steiner's excellent conclusion: how did Hitler triumph over a nation as well-educated, culturally advanced and highly industrialised as Germany?

Piers Brendon's books include 'The Dark Valley: a panorama of the 1930s' (Pimlico)