In October 1916, as the war in Europe was entering its third terrible year, President Woodrow Wilson remarked that “a hundred years from now, it will not be the bloody details that the world will think of in this war: it will be the causes behind it, the adjustments which it will force.” He may have underestimated future generations’ fascination with the “bloody details” of the fighting, but about our persistent interest in the war’s causes and consequences he was surely right. As we get ready to mark the centenary of the outbreak of war in 1914, there is general agreement about its consequences: it was what George Kennan once called the twentieth century’s “seminal catastrophe.” The causes of this catastrophe, however, remain the subject of intense debate.

Disagreements about the causes of the war began before the first shots were fired, as the various belligerents rushed into print with documents that demonstrated their own innocence and their opponents’ guilt. In 1919, the peace treaty imposed upon the defeated Germans contained an article that seemed to make them responsible for the war and its consequences. Within a decade, however, disillusionment with the peace settlement encouraged contemporaries to spread the blame to every government. In 1929, for example, Virginia Woolf did not distinguish between winners and losers when she recalled “the faces of our rulers in the light of the shell fire. So ugly they looked—German, English, French—so stupid.” In 1961, the debate on the war-guilt question was given new energy and direction by the German historian Fritz Fischer, who asserted German guilt and thereby connected the catastrophe of 1914 with yet more horrific catastrophes of 1939–45. In a series of densely documented books, Fischer and his followers insisted that it was not collective stupidity that pushed Europe over the brink in 1914, but rather planned aggression that sprang from deeply rooted flaws in Germany’s political and social structure. Although Fischer’s work was vigorously criticized when it first appeared, and lacked unanimous support from historians, by the 1970s it had become the basis for a rough scholarly consensus that assigned Germany a predominate share of the blame for starting the war. Over the past decade, that consensus has begun to unravel. Four new books suggest that the centenary has reopened the question of why Europe went to war in 1914.

Debates about the immediate causes of the war focus on the period between the assassination in Sarajevo of the heir to the Habsburg throne, Archduke Franz Ferdinand, on June 28, and the formal declarations of war five weeks later. Seven nations were directly involved: the great powers (Austria-Hungary, Germany, Russia, France, and Britain), the kingdom of Serbia, whose agents seemed to be behind the archduke’s murder, and Belgium, whose invasion by German troops ensured British participation. In all those states, decision-making was in the hands of a relatively small group of men—heads of state and their advisers, senior ministers, diplomats, and military leaders. Sean McMeekin’s helpful list of the dramatis personae contains eighty-five names. About what these men thought and did between June 28 and August 4 we know an immense amount—from government memoranda, diplomatic dispatches, newspaper reports, and a library of diaries and memoirs published after the war. Of course, as Christopher Clark notes, “there are treacherous currents in this ocean of sources.” Even when they are not willfully misleading, the contemporary documents are necessarily distorted by their authors’ personal foibles, political interests, and institutional bias. None of the major players fully understood what their counterparts were doing; none of them recognized the full implications of their own actions. And if the authors of these contemporary documents knew too little, when they penned their memoirs, they knew too much. Writing in the harsh light of the postwar disillusionment, every participant tried to minimize his own responsibility for the disasters.

In July 1914, Sean McMeekin, an American historian who teaches in Turkey, provides a day-by-day, sometimes hour-by-hour, account of the crisis that began with the assassination in Sarajevo. By keeping his account close to the shifting contours of the crisis, he is able to capture its human dimensions. Better than any of the other books reviewed here, he gives his readers a sense of how events looked to the participants as they struggled to make sense of what was going on. At the same time, he carefully weighs each piece of evidence, offering alternative interpretations before stating his own firmly held opinion.

The first, and in many ways decisive, step toward war was taken in Vienna, when the Austrian government decided to move against the Serbs, whom it suspected, not unreasonably, of being involved in the archduke’s murder. This, the Austrians knew, carried the risk of war, not only against Serbia but also against Russia, Serbia’s patron and protector. This was a risk they could not take without German support, which they received early in July. Germany’s unqualified willingness to back Austria was critically important for what happened next: as virtually every historian agrees, without it there would have been no European war. The disagreement is about German motivation. While Fischer and his supporters argued that Germany eagerly pushed for a war they had long wanted, McMeekin stresses the confusion and uncertainty that pervaded decision-making in Berlin. “Far from ‘willing the war,’” he concludes, the Germans were dragged “kicking and screaming” into the conflict by their Austrian partner. Moreover, he does not assign Russia and Russia’s ally France merely passive roles in the final crisis; in fact, they were “far more eager to fight than was Germany.” Among these four authors, McMeekin is the most emphatic about the long-term significance of the July crisis. Without it, he maintains, there would have been no war in 1914 and perhaps not in the immediate future. If anything, when the archduke was killed relations among the great powers were getting better, not worse.

In contrast to McMeekin’s disciplined, focused narrative, Margaret MacMillan’s The War that Ended Peace takes us on a leisurely tour of European history in the decades before the war. A Canadian who is professor of international relations at Oxford, MacMillan displays the same virtues that made her Paris 1919 so successful: graceful prose, a good eye for the telling anecdote and colorful personality, and a keen appreciation for the underlying ironies of the past. At times, she is distracted from her central story by the inherent drama of unrelated events: the Dreyfus affair, for instance, to which she devotes several stirring pages, had nothing to do with the origins of the war.

MacMillan provides a moderate, balanced analysis of why peace ended: Austria was the prime mover, with Germany its willing but not actively aggressive accomplice; Russia’s impatient and provocative response to the Austrian challenge to Serbia made matters worse. France and Britain were reluctant and largely passive participants. She correctly notes a certain complacency among statesmen who thought the crisis could be managed, as had so many in the past, a complacency that was not dispelled until too late. And she is right to insist that the advocates of peaceful accommodation were everywhere more hesitant and divided than those who wanted to fight. At times, the emphasis and organization of MacMillan’s book seem inconsistent with her explicit argument. Germany, and especially Germany’s rivalry with Britain, gets a disproportionate amount of attention. The Anglo-German antagonism, however, while of great importance for how the war was fought and why the Germans lost, did not play a major role in 1914.

IN THE SLEEPWALKERS, Christopher Clark, an Australian who teaches at Cambridge, skillfully weaves together the unfolding of the July crisis with long-term trends in the international system. The foundation of Clark’s achievement is his recognition that the place to look for the war’s origins is where it actually began, in the unstable political landscape of Southeastern Europe. Clark begins his account not with the murder in Sarajevo (as do McMeekin and Hastings), nor with the burning of the Belgian city of Louvain by German troops (as does MacMillan), but with the brutal murder of the Serbian king and queen by dissident army officers in 1903, which produced a profound shift in Serbia’s international alignment away from Austria and toward closer cooperation with Russia. Serbia in the early twentieth century can be compared to present-day Pakistan: a fragile civilian government, a powerful military, unfulfilled territorial ambitions, and a security service that pursued its own agenda. Within a secret cell of Serbian officers the plot to kill Franz Ferdinand was hatched and implemented.

Better than any other book I know, The Sleepwalkers convincingly traces the causal chain that linked this isolated act of state-sponsored terrorism to the outbreak of the first war involving all of Europe’s great powers since the defeat of Napoleon in 1815. The most important link in this chain was the system of alliances that divided Europe into two camps, whose political agreements were eventually supplemented by military cooperation. Once Anglo-French naval strategy and Franco-Russian mobilization plans became mutually interdependent, the chances of localizing a war between the great powers were substantially reduced. By 1914, France was willing to underwrite Russian engagement in the Balkans, where Ottoman decline fed the aggressive ambitions first of Italy, which launched a war of conquest against the Turks in 1911, and then of Serbia, Bulgaria, Rumania, Greece, and Macedonia, which fought the Turks, then one another, in 1912–13. Meanwhile, Germany, alienated from France, unable or unwilling to reach an agreement with Britain, and worried about Russia’s growing military power, became increasingly dependent on its only reliable ally, Austria-Hungary. Not to support Austria in July 1914 was to risk being left alone to face a coalition of hostile powers.

None of those developments made war inevitable. There were, Clark shows, always other possibilities; chance, miscalculation, personal frailties all played a role. But in the end, policymakers did decide to stand up to their opponents, support their allies, and accept the advice of those who insisted that war was necessary, victory possible, retreat unthinkable.

My one complaint about Christopher Clark’s superb book is its title. The men who led their nations to war were not sleepwalkers; they were wide awake, fully conscious of what they were doing. With varying degrees of enthusiasm, they all eventually decided that war was preferable to diplomacy. But of course the war that Europe’s leaders actively sought or reluctantly accepted was not the war they got. Why this was so is the subject of Max Hastings’s Catastrophe 1914.

After a relatively brief and rather conventional account of the origins of the war, Hastings turns his attention to the first four months of the fighting, which, as we should expect from one of the world’s finest military historians, he describes brilliantly—no one is better at depicting the intimate details of combat without losing sight of the big strategic picture. Hastings points out that while all the armies suffered in these opening battles, none suffered as much as France, whose soldiers, still wearing the bright uniforms of an earlier era, were slaughtered at a truly appalling rate. In just three days, between August 20 and 23, forty thousand Frenchmen were killed. By August 29, with the war less than a month old, the French had suffered over a quarter-million casualties, including seventy-five thousand dead.

Hastings is unsparing in his criticism of the military leaders who prepared for and presided over this bloodbath. There was, he writes, a constant “mismatch between the towering ambitions of Europe’s warlords and the inadequate means with which they set about fulfilling them.” Hastings’s treatment of the British commander Sir John French is particularly harsh, but surely the worst of this bad lot was Franz Conrad von Hötzendorf, the chief of the Austrian general staff, whose hearty appetite for war was matched by his extraordinary strategic incompetence. Only Joseph Joffre, the French general whose stubborn resolve managed to halt the Germans at the Marne River in September, earns Hastings’s somewhat reluctant admiration.

BY CHRISTMAS 1914 the war the generals had expected, a war of massive deployments and offensive engagement, was over. What they had not expected was that no one had won. Because neither side was able to break out of the strategic trap in which they were inexorably caught, the fighting dragged on until one collapsed. “Both armies,” Hastings writes, “possessed unbounded power to inflict losses and grief upon each other; but as long as each had men and guns, the defense could be reinforced faster than the attackers could exploit local success.”

Hastings is the only one of the four authors to argue unambiguously that, for all its horrors, the war was worth fighting and, once begun, had to be won. He sharply dissents from “the indulgent view of some historians that a German victory…would have represented the triumph of a nation and a cause morally indistinguishable from those of the allies.” A German victory had to be prevented and, Hastings insists, the only way to do this was to defeat them on the battlefield. From the British perspective, that is a defensible if not wholly convincing argument. But viewed from the rest of Europe, it is difficult to imagine how anything, even a German victory, could have turned out to be worse than what actually did happen after 1918.

Such speculation suggests a question every bit as perplexing as why the war began: Why was it allowed to go on so long, consuming quantities of blood and treasure far beyond any possible advantage? While their young men died and their loved ones mourned, why did Europe’s leaders persist in this folly? Why were so few voices raised against it? Why did every statesman continue to find that is was easier, more expedient, even more reasonable to demand ever greater sacrifices rather than to admit that the sacrifices made so far would be in vain? These failures of moral imagination and political will, spread across the political landscape from London to Petrograd, doomed Europe to three decades of totalitarian terror and racial murder.