One night in early 1998, two dozen American soldiers from Delta Force lay in wait by the side of a Bosnian mountain road to ambush the Bosnian Serb war criminal Radovan Karadžić. According to a tip-off, Karadžić would be passing en route to a meeting within the next 48 hours. In order to take him alive and avoid a shootout with his four experienced bodyguards, the team had needed a plan that prioritized the element of surprise. To that end, they proposed to make use of three custom-made props: a 10-foot mat studded with razor-sharp titanium spikes capable of puncturing the tires of Karadžić’s car, a sausage-shaped grenade that would blow off the doors and concuss its occupants—and, as the bizarre pièce de résistance, a gorilla suit.

As the soldier who came up with the idea put it, “The shock of seeing a freaking gorilla walking down the road, along with their uncontrollable curiosity to understand what the hell it’s doing in the middle of Bosnia, may just make them pause a couple more seconds, which ought to create the perfect conditions for us to fire the rounds and conduct the capture.”

But despite these best laid plans, and the reliability of Delta’s informant, the capture didn’t happen because Karadžić failed to show up, either that night or the next. For fear of being compromised, the team was told to stand down and disband. Karadžić, the Bosnian Serbs’ political leader, together with his military commander Ratko Mladić, would remain at large for another decade and become Europe’s most wanted men.

The long and troubled attempt to track down, arrest, and bring to justice those responsible for unleashing carnage on the people of the former Yugoslavia is at the heart of an engrossing new book by Julian Borger, the diplomatic editor for the Guardian who covered the Bosnian War of the ’90s for the paper and the BBC. On one level, The Butcher’s Trail: How the Search for Balkan War Criminals Became the World’s Most Successful Manhunt is a chronicle of 14 years of false starts, divided loyalties, inherent dangers, and occasional scandals. But ultimately it is the tale of a historic and productive campaign conducted by tireless and fearless investigators who, over time, managed to catch the perpetrators of the worst crimes against humanity committed in Europe since the Nazi era.

Borger opens with a brief history about the disintegration and dismemberment of “the exhausted federal experiment” that was Yugoslavia. Serbia emerges as the most predatory of the constituent republics, with its leader, nationalist despot Slobodan Milošević, ruthlessly creating a Greater Serbia at the expense of his neighbors. This involved seizing towns and then ethnically cleansing them. The most infamous atrocity was the Srebrenica massacre in 1995, in which 8,000 male Bosnian Muslims were killed by Bosnian Serb units under Mladić and on orders from Karadžić. Finally, after looking the other way for too long, the international community sat up, paid heed, and took action.

Not that it had been completely idle. In 1993, a special court, the first international tribunal of its kind since the Nuremberg tribunal, was set up by the UN in The Hague and tasked with pursuing and indicting war criminals. The International Criminal Tribunal for the former Yugoslavia drew up a list of suspects ranging from past prison guards to ex-presidents. A ragtag alliance of intelligence agencies and special forces troops from six countries worked entirely in the shadows following trails of blood, some freshly spilled, some almost dried up. Borger notes that it was, quite literally, a manhunt: There was only one woman on the ICTY’s list and she turned herself in. By 2011, all 161 fugitives on the list faced justice one way or another.

Borger’s opening chapters deal with messy maiden arrest missions by the British SAS and Dutch marines, and American failure due to lack of resources and distrustful relations with their French allies. Many of their targets are small fry rather than big fish. Some they spirit away to The Hague for sentencing, others are shot before they can be snared.

Gradually, though, after much reorganizing and re-energizing, the hunters home in on and take alive higher-ranking suspects. In 1998, American SEALs arrest Goran Jelisić, a young but sadistic prison-camp guard who would brazenly introduce himself to new inmates as “the second Adolf.” In 1999, the SAS bag the biggest prize of their campaign, one Gen. Stanislav Galić, who oversaw the daily sniper fire and shelling of the people—civilians, not military personnel—of Sarajevo. And in 2000, the CIA employ Serb bounty-hunters to grab Dragan Nikolić, a concentration camp commander with a predilection for beatings and torture, who later admitted that many of his victims were “people who used to be friends of mine, whom I used to see over the years in cafés, on sports fields, and playgrounds, with whom I spent summer vacations.”

Borger goes on to show how Croat forces were also responsible for war crimes in Croatia and Bosnia. After the war, and after some reluctance, the Croatian government played ball with The Hague and handed over suspects. In return, Croatia was formally recognized as a candidate for EU membership. However, by the time ICTY prosecutors had gathered enough evidence to implicate the father of modern Croatia, President Franjo Tudjman, in crimes of persecution, rape, and murder, was long dead from stomach cancer.

Other suspects die from natural causes or by their own hand before they can be tried. Such instances of thwarted justice make for frustrating reading. A section on American forces prioritizing the capture of more-heavyweight criminals, in particular the participants in the Srebrenica massacre, takes the reader through several emotions. There is anger and revulsion at the level of mass murder that Bosnian Serb troops got away with and for so long (“Kill them all. God damn it,” was the hysterical command of one vengeful general). There is excitement as Delta units close in on targets, and there is cathartic relief as snatch plans are effectively carried out. But there is also disappointment as U.S. forces take stock and realize that despite their success, they have failed to achieve their stated objective of finding leaders.

“We had the tradecraft, we had the equipment and training, but we didn’t have an understanding of the terrain,” opines one Special Operations Forces officer. After 9/11, the Bosnian manhunt is relegated to the back burner, with terrorists replacing war criminals as targets, and the Balkan playing field giving way to the Afghan battleground—a shift from one terra incognita to another.

In one welcome chapter, Borger veers away from the male-dominated realm of hunter and quarry to focus on two tenacious female ICTY prosecutors, Louise Arbour and Carla Del Ponte. Both women weathered criticism and apathy to ensure the Balkan manhunt continued (with Del Ponte even jumping into Condoleezza Rice’s car to appeal for her support). But they also fielded abuse and death threats. Arbour became an assassination target for nationalist networks in Serbia and Croatia. The press and political figures of both countries branded Del Ponte a whore. Rampant nationalism, Borger writes, mutated easily into savage misogyny. Undaunted, the pair continued to fight their campaign, and at the end of their tenure left an important concrete legacy—the ICTY’s own tracking team.

The last, thrilling third of the book is the equivalent of a big-game hunt: the intensified search for and capture of the wretched triumvirate—Milošević, Karadžić, and Mladić. After 200 pages witnessing the arrest and conviction of middlemen in the killing factory, finally we come upon the top brass. Borger replays Milošević’s ignominious fall from power and charts his arrest and subsequent delivery to The Hague by the democratically elected government that had ousted him. In conversations with his jailer about his role as the protagonist of four disastrous Yugoslav wars and the orchestrator of large-scale slaughter of innocent civilians, Milošević shows no remorse, seeing himself not as the losing villain but the “moral victor.”

Milošević was there for the taking, but Karadžić and Mladić remained elusive fugitives, even with $5 million bounties on their heads. At one point, a somewhat cocky Karadžić boasted that it would “take a battalion” to find him and get to him through the Preventiva, his group of bodyguards. After the night Karadžić failed to appear and be rattled by the sight of a gorilla on the road, there was a further American attempt to get the “Serb Pimpernel” by way of an offer of immunity and money to his longtime driver in return for betraying his boss. But the driver panicked, believing the proposal to be a ploy of Karadžić’s to test his loyalty. When that plan backfired the trail went cold. “The shambolic poet-psychiatrist-warlord-gambler managed to stay one step ahead of the enormous military and intelligence effort to find him.”

But his luck ran out in 2008. An intercepted phone call led investigators to a high-rise apartment block in Belgrade, the address of a white-bearded New Age mystic. Alarm bells rang when it transpired that this shaman was in contact with Karadžić’s younger brother, and that he carried half a dozen cellphones, some of which were used to maintain contact with hardline Serb nationalists. He was grabbed while traveling on a bus—“a banal end to a life on the run that Karadžić himself had envisioned in almost mythic terms, his people’s last hope hiding in plain sight from a legion of oppressive foes.” Like Milošević, once at The Hague he denied any wrongdoing and assumed the role of a Serb martyr.

Equally tense and explosive is the account of Mladić’s last days of liberty. Borger explains how over 14 years the pugnacious general was shielded by various groups and institutions: first by the Serbian military establishment, then a close-knit gang of Bosnian Serb wartime lieutenants, and, finally, his beleaguered family. In case any of his minders considered turning him in for the $5 million bounty, Mladić would present them with gift-wrapped portraits of their children or grandchildren—a chilling reminder that he knew where they lived and went to school. In 2011, in another bathetic finale, Mladić was traced to a rundown farmhouse in a small town in northern Serbia. Unlike Karadžić, who opted for disguise and an alias, and pleaded mistaken identity, Mladić comes clean to his captors. “You have found who you’re looking for,” he boldly proclaims. “I’m Ratko Mladić.”

The Butcher’s Trail achieves the dual feat of being both informative and gripping. Borger’s thorough research comprises numerous books, articles, and recently declassified documents on the Balkan conflict and international justice but also first-hand interviews with key players: former soldiers, intelligence officials, investigators, prosecutors, and diplomats from a dozen countries. In addition, Borger impresses by not only divulging facts and dropping shocking revelations (Vladimir Putin’s spy agency, the FSB, took a pro-Serbia stance and protected Mladić) but also analyzing testimonies, evaluating the various mindsets of criminals on The Hague’s list and weighing up conspiracy theories. He even provides close readings of Karadžić’s doggerel poetry—art of the same caliber as Hitler’s watercolors—for indications of inner tumult and hints of future crimes.

Borger ends his history on a bittersweet note. First of all, he is sanguine about the course of justice. Despite the over-long process, the two bloodthirsty Bosnian Serb leaders are on trial for genocide and war crimes and will, at some juncture, be judged and sentenced. However, Borger soon slips in a sobering truth: more and more of Karadžić’s and Mladić’s henchmen are being either acquitted or released after having served only two-thirds of their sentences. Worse, they are returning home to a hero’s welcome—a motorcade drive past cheering, flag-waving crowds. In one instance, a Catholic bishop performed a thanksgiving Mass. Nationalism is on the rise, Borger concludes—if it ever went away—and the crimes of the past are being erased. Perpetrators routinely play the victim card; their supporters stick their heads in the sand and slather unsavory facts with a thick layer of revisionism and denial.

And yet Borger offers a discernible silver lining. He argues that the detailed record of the tribunal, with its 7 million documents, cannot be ignored. Nor can the demand for justice for egregious war crimes. And it is justice—the need for it, a championing of it—which lies at the heart of his book. The ICTY demonstrated that war criminals could be tracked down, pulled out of hiding, or wrenched out of complacency, and punished for their deeds. Indeed, to this day, the ICTY is still the high-water mark of international justice for crimes against humanity, the benchmark against which all similar endeavors in the future will be judged.