Apologies to all you World Cup fans, but today I am concentrating, briefly, on less uplifting matters. In Iraq on Sunday, the Islamic State of Iraq and al-Sham proclaimed the establishment of a caliphate extending from western Iraq through parts of Syria, areas it already largely controls. “This is not the first border we will break, we will break other borders,” a jihadist boasted in an English-language video called “End of Sykes-Picot,” which was posted on (and subsequently removed from) YouTube. Meanwhile, here in the United States, intelligence experts warned that terrorists trained in Syria and Iraq may be preparing to launch attacks on Western airliners with new hard-to-detect bombs.

These events came a day after the citizens of Sarajevo marked the hundredth anniversary of the shot that led to the outbreak of the First World War: the assassination of Archduke Franz Ferdinand, of Austria, by Gavrilo Princip, a young Serbian nationalist. After the Archduke’s murder, it took about six weeks for Germany and Austria (the members of the Dual Alliance) and Britain, France, and Russia (the members of the Triple Entente) to declare war on each other, and another two years of unimaginable bloodshed for the British and the French to finalize the secret Sykes-Picot Agreement, which laid out a division of the Arab provinces of the teetering Ottoman Empire into French and British zones. These eventually became the countries we now know as Syria and Lebanon (the French bits), and Iraq and Kuwait (the British bits). The road linking Sarajevo to Baghdad was a long but direct one.

So, it was historically fitting for the propagandists of ISIS to mark the hundredth anniversary of Archduke Ferdinand’s death by tearing down—or, at least, saying that they’d torn down—one of the last vestiges of what became known as the Great War. The Sykes-Picot Agreement was exposed by the Bolsheviks in 1917, and has been, ever since, a symbol of Western imperialism and perfidy for many in the Middle East. Prior to the war, the British government, in the personage of Colonel T. E. Lawrence and others, had promised Arabs a homeland of their own in return for taking Britain’s side against the Ottomans. But, when push came to shove, the colonialists acted true to form.

My purpose here is not to throw stones, lay blame, or provide a justification, of any sort, for the horrendous violence and fanatical ideology of the jihadis, whose promised land is a sectarian, sexist dictatorship—a totalitarian negation of the Enlightenment. My point, on this anniversary, is simply to restate an elementary lesson of history that we’ve recently relearned to our cost. Wars are terrible things, and they have terrible, unpredictable consequences.

The terrible bit, it is true, never entirely left the public consciousness. In northern England, where I grew up, every town and village had monuments to the victims of the Great War, and of the even greater conflict that followed it just twenty years later. Here in the United States, we have Memorial Day, the Holocaust Museum, and the Vietnam memorial. That is at it should be. From the Somme to Dresden to Hiroshima to the killing fields of Vietnam and Cambodia, the reality of total war, a phenomenon pioneered by the Union and the Confederates but perfected by the Europeans, is impossible to forget, or ignore.

Somewhere along the line, though, some of our politicians and foreign-policy “experts” forgot about, or willfully ignored, the unpredictability of modern warfare. If there’s one thing that almost all accounts of those fateful weeks in 1914 agree upon—from A. J. P. Taylor’s “War By Timetable” to Christopher Clark’s “The Sleepwalkers: How Europe Went to War in 1914”—it is that the politicians, diplomats, and military planners of the time had no conception of the world-altering catastrophe that was about to unfold. Despite an epic arms race that had developed over the previous ten years, many of them still thought of warfare in the eighteenth- and nineteenth-century sense of pursuing strategic ends by military means.

In Germany, for instance, elements of the Kaiser’s government and the Prussian officer class were convinced that their young and rising country, hemmed in by France and Russia on land, and by the British at sea, needed to establish, once and for all, its right to define and dominate a Mitteleuropa. When turmoil broke out in the Balkans following the Archduke’s assassination, according to the thesis put forward in 1961 by the German historian Fritz Fischer, the Germans exploited the situation for their own ends, hoping that they could knock off France and Russia while keeping Britain out of the conflict.

It didn’t work out like that, of course. With Germany’s military machine growing by the year, British defense experts advised Herbert Asquith, the Liberal Prime Minister, that this might be the final opportunity to confront the Kaiser. Asquith, one of the few politicians who had a realistic view of the dangers that lay ahead, swallowed his doubts and honored Britain’s commitments to Belgium and France. By the time the Germans were finally defeated, four and half years later, about twenty million people were dead, the horrors of poison gas and other technologically advanced methods of killing people had been exposed, and the entire European order, which, in those days, meant the world order, had collapsed. Out of the wreckage, and a vengeful peace treaty, arose the Nazis and the Bolsheviks.

Eric Hobsbawm, the late British historian, was surely right to group together the years from 1914 to 1991 as the “Short Twentieth Century.” In an important sense, the period from Princip to the rise of Boris Yeltsin represented the playing out of forces that the Great War unleashed. Then the Soviet Union collapsed, and the short century ended. After a brief period of hope and American triumphalism came the U.S.-led invasion and occupation of Iraq.

Here is not the place to dwell, at length, on the debates surrounding that folly and its denouement. In scale and ultimate import, the Great War and the Iraq War cannot be compared. The Middle East is but one region of the world, and it was a troubled one well before George W. Bush left Texas. But it is surely apt, on this anniversary, to note one historical analogy. The disastrous aftermath of the Iraq misadventure demonstrated once again the law of unintended consequences.

During the nineteen-nineties, with the Soviet empire defunct, and the threat of nuclear annihilation seemingly gone with it, the nineteenth-century notion of limited warfare made an untimely comeback in parts of Washington. Then, in the aftermath of 9/11, the United States government decided to demonstrate its military might and reconfigure its strategic situation. Some deluded souls said that the American troops would be cheered into Baghdad, and, on the ashes of Saddam’s regime, a model democracy would be built.

As in 1914, these prewar hopes didn’t survive for more than a few weeks of actual conflict. The decision to go to war unleashed demons that took events in directions that could never have been imagined, one of which eventually involved a well-armed group of religious fanatics seizing large chunks of territory in Iraq and Syria, trampling on the Sykes-Picot settlement, and threatening Baghdad. (All this on the eve of the World Cup, a largely benign exercise in nationalist excess.)

Where things go from here, God, or the roulette wheel of history, only knows. But, over the next few weeks, as you watch the solemn ceremonies marking the anniversary of 1914, it is worth recalling the old truism that one thing leads to another. And, in warfare, that other thing is usually a tragedy.

Photograph by Dado Ruvic/Reuters.