Milorad Dodik, the former president of Republika Srpska, the Serb half of Bosnia-Herzegovina, is building closer ties with people associated with U.S. President Donald Trump. | BLOOMBERG

U.S. President Donald Trump has been a boost for a number of leaders across the world, but few in Europe relish their alliance with him and his entourage as much as Milorad Dodik.

Ostracized by the European Union and sanctioned by the U.S., the most enduring politician in Bosnia-Herzegovina backed Trump from the start. Over the years as president of the Serb half of the country, he built ties with Trump’s family and friends, got his U.S.…