While Europe focuses on the war in Ukraine and the prospect of pared-back American security assistance, trouble is brewing in the southeast corner of the continent. Three decades ago, in November 1995, the U.S.-brokered Dayton accords ended the Bosnian war, a three-and-a-half-year ethnic conflict that killed roughly 100,000 people and displaced two million. The settlement imposed a complex power-sharing structure on a divided country, promising the state of Bosnia and Herzegovina a new start.

Europe and the United States led the charge to safeguard the carefully crafted peace. Yet that oversight has eroded in recent decades, as both Brussels and Washington turned their focus elsewhere. The absence of international pressure has emboldened nationalists within Bosnia such as Milorad Dodik, a Bosnian Serb leader who has repeatedly called for the secession of Republika Srpska, the semiautonomous region where he served as president. Dodik was banned from holding public office in 2025 and has faced U.S. sanctions since 2022. In late October, however, the Trump administration lifted those sanctions. The decision appeared to be an act of patronage by President Donald Trump: Dodik’s government had hired several Trump associates as lobbyists, including former Illinois Governor Rod Blagojevich, who argued that the sanctions amounted to political persecution. But it also reflected a long-running shift in U.S. policy, with the United States stepping back from the commitments it made to Bosnia three decades ago.

Unless Bosnia’s international partners start paying more attention, Dodik and other nationalist leaders will continue to erode Dayton’s constraints on ethnic autonomy and secessionist ambitions. The United States’ retreat from Bosnia is unlikely to reverse any time soon, so responsibility for the country’s political future now rests squarely with European leaders. If Europe cannot reclaim its role as a guarantor of stability and promoter of reform, it risks watching Bosnia’s fragile balance give way altogether. The failure of the Dayton accords would threaten European security, further damage the EU’s credibility, and legitimize the perception—already exploited by Russia in Ukraine—that borders and agreements can be revised by force.

The Bosnian war erupted in 1992, when Bosnia and Herzegovina, a multiethnic territory composed of Bosniaks, Croats, and Serbs, declared independence from Yugoslavia. Serbian President Slobodan Milosevic—Serbia was another constituent republic of Yugoslavia—objected to the move. From his perch in Belgrade, he offered political and military support to Bosnian Serb leaders who fought to secure Serb-controlled territory across Bosnia and prevent Bosnian Serbs from falling under the authority of a new Bosnian state. It plunged the country into a brutal war marked by ethnic-based violence and mass atrocities committed against civilians.

Thirty years after the end of the war, the guns have stopped, but, so too, has Bosnia’s progress. The country is riven by divisive identity politics and patronage networks. The economy has stalled, as has Bosnia’s movement toward European integration. Corruption is rampant. Young people leave the country at alarming rates, and Bosnia’s population is smaller today than it was at the end of the war.

Many blame Dayton’s power-sharing arrangement. Every major institution is designed to serve the country’s three main constituent ethnic groups rather than a single Bosnian citizenry. The country therefore has three presidents; two semiautonomous entities, the Bosniak- and Croat-dominated Federation of Bosnia and Herzegovina, which itself is divided into ten cantons split between Bosniaks and Croats, and the Serb-dominated Republika Srpska; and an independent district. Each political entity has its own bureaucracy. It is because of this structure that Bosnia has little coherent national policy; there are, for instance, 13 education ministries within the country. The ethnic power-sharing system was meant to prevent domination by any one group and to force cooperation among former enemies. Instead, it has produced political polarization that paralyzes the country’s development.

The accords also included measures to keep the country from returning to........

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