I first went to Bosnia in 1992 to cover Europe’s worst war since Hitler’s war. Like many others I came away scarred at the war’s end in 1995. The scars, in my own case, were not physical but they were deep, composed not only of the horror itself, but of living with the failures of Western states and the United Nations that led to the Srebrenica massacre.

Srebrenica was a disaster foretold. The slaughter by Serb soldiers of about 8,000 Bosnian Muslim men and boys, beginning on July 11, 1995, took place more than three years into the war. It unfolded in a United Nations “safe area” that proved to be anything but that, in a country patrolled to no discernible effect by NATO jets, and in a context of endless evasion by Western governments reluctant to intervene.

The slaughter at Srebrenica was proof, if any were needed, that good intentions alone do not save lives.

To live in Sarajevo, a besieged European city with a dirt trench around it, and to travel through Bosnia, was to experience, again and again, the blank gaze of the dead, the ravages of shrapnel, the grimace of roofless homes and the cries of brave women attempting to shelter their children.

Bosnia was a mixed society when the war began. The attempt led by Radovan Karadzic, the now imprisoned leader of the Bosnian Serbs, to replace such mingling with an ethnically pure Serbian preserve took more than 100,000 lives as Bosnian Muslim and Croatian forces eventually fought back.

For three years, after the initial Serb ethnic cleansing and slaughter of the Muslim population of Bosnia in 1992, the international response was feeble. When, thanks to the work of Ed Vulliamy of The Guardian and an ITV news crew, photographs emerged of emaciated Bosnian Muslim prisoners held at the Serb camps of Trnopolje and Omarska, outrage subsided into a collective shrug. Yet these images recalled the worst crimes of the 20th Century.

“The truth is, people there keep killing each other,” President Clinton said in early 1994. There was nothing, in other words, to be done about war in the benighted Balkans.

Thirty years on, with another war raging on the European continent, photographs from that time contain at once a disturbing familiarity and a transporting power: the etched rib cages of starved Bosnian Muslim prisoners; a panicked woman dashing across a Sarajevo intersection with a small child in her arms; the blasted buildings of the besieged Bosnian capital; the grief-stricken exasperation of a woman from Srebrenica confronting a U.N. soldier’s impassivity; the interlaced corpses of Muslims, dumped in a mass grave and killed for being Muslim.

Gazing at these images, I hear again, three decades on, the flat boom of rending and fracture that is the sound of another shell’s impact, and feel again a familiar knife in the gut. Fear contracts the stomach. Some experiences do not leave you. For a generation of journalists, Bosnia was a turning point.

I learned, covering this war, that hatred is an elixir, a potent political bomb, a seductive answer to the banality of life. It ushers the lone individual into a consoling tribe. It is always available to the nationalist demagogue ready to identify scapegoats, promise vengeance and whip a pliant population into a frenzy.

Bosnia taught the potency of history as tormentor and torch. Slobodan Milosevic, the Serbian nationalist leader, convinced the Serbs that the Muslims of Bosnia were the Ottoman Turk enemy of old. They went to work to excise the Muslim interlopers, as they saw them. The fact that a few years earlier their victims had been unremarkable fellow Yugoslav citizens was swept away in the nationalist tide.

The Serb-encircled enclave of Srebrenica, protected in theory by more than 400 Dutch U.N. troops, suffered the culminating assault of this Serbian campaign. Humanitarianism has an inherent preference for neutrality, for succoring the victim rather than confronting the perpetrator. So may “impartiality” incubate disaster.

Dutch supplies of fuel and ammunition were low because the Serbs repeatedly blocked their arrival. To the last, U.N. generals at the head of the United Nations force in Bosnia were reluctant to believe that the Serbs would overrun a “safe area” and kill every Bosnian Muslim male in their path.

Yet they had done virtually the same thing in nearby eastern Bosnian towns like Vlasenica, cleansed of its Muslim population in 1992; indeed Srebrenica was full of refugees from this earlier assault. There were precedents, but nobody with the capacity to stop the genocide had the courage to draw appropriate conclusions from them.

The massacre that followed was both systematic and pell-mell, carried out secretively and in plain sight. It took years for bodies to be unearthed and for missing loved ones to be identified, if they ever were, and eventually, often many years later, to be reburied with dignity.

The grief I encountered in Tuzla among Bosnian refugees who fled there from Srebrenica, almost all of them women and children, was overwhelming. They had lost everything, their husbands and fathers and brothers most immediately, but also any faith in civilization and the resolve of the West to stop war on the European continent.

Time has suggested they were not wrong. The photograph of Ferida Osmanovic, a young mother from Srebrenica who hanged herself in a forest after her husband’s disappearance in the midst of the massacre, is a stark portrait of what the world’s betrayal wrought.

The photograph became a potent symbol of failure. It prompted questions in the U.S. Senate and led Vice President Al Gore, prodded by his dismayed daughter, to ask, “Why is this happening and we’re not doing anything?” The Srebrenica massacre, denied and never fully acknowledged in Belgrade, remains an admonition to us all.

The genocide, recognized as such by the International Criminal Tribunal for the Former Yugoslavia, hastened the war toward its conclusion by shaming Western governments into action. NATO bombed the Serbs in late August and September 1995. Milosevic, the all-powerful, crumpled. Peace followed later that year with an accord signed in Dayton, Ohio, after Richard C. Holbrooke led a relentless American diplomatic effort. Forceful Western intervention worked in this case, lest anyone forget.

It was a dismal peace, one that came far too late and left Srebrenica in the Serb part of Bosnia, but it stilled the guns. It could not, however, assuage the enduring agony of the town, as the tormented expressions of the bereaved demonstrated at a mass burial in 2005 of 610 victims of the massacre. Absent Serbian admission of the crime, reconciliation and closure have proved impossible.

Yugoslavia, the state of the South Slavs, grew out of the collapse of the Habsburg and Ottoman empires during World War I. It disintegrated under attack from the Nazis, coalesced again around the dream of Communism, held together under the firm hand of Josip Broz Tito’s one-party Communist rule, only to die in the resurgence of nationalism ushered in by the collapse of the Soviet Union. The most destructive themes of what Isaiah Berlin called “our most terrible century” were caught in Yugoslavia’s 73-year trajectory: the end of empire, the ravages of Fascist terror, the rise and fall of Communism, and finally the nationalist fever of post-Communist societies.

Recalling Srebrenica, contemplating Ukraine, it is clear that a central challenge of our times is to ensure that one terrible century is not followed by another, for the embers of murderous nationalism still burn.