For years, people have gathered in March in the eastern Bosnian city of Visegrad to mark the capture of Dragoljub "Draza" Mihailovic, the controversial Serbian general who led the World War II nationalist Chetnik movement, some of whom collaborated with Nazi forces.
This year, they went too far.
The 200 or so who met on March 10 paraded with some singing songs that included lines such as "there will be hell, the River Drina will be bloody, here come the Chetniks from the Serb mountains."
That crossed a line with many Bosnian Muslims, legal experts, and even Western diplomats, prompting the state prosecutor on March 12 to announce an investigation into the incident.
"The complaints refer to a criminal offense -- provoking national, racial, and religious hatred, discord, and intolerance under Article 145a of the Bosnian Criminal Code," the prosecutor’s office said.
For decades, Mihailovic has fueled division in both Bosnia-Herzegovina and Serbia.
His backers view him as a national hero who died for political reasons. His critics say he collaborated with the Nazi occupiers. Non-Serbs in the former Yugoslavia accused his troops, known as Chetniks, of committing numerous atrocities.
In 1941, as a Yugoslav royal army officer, Mihailovic launched a resistance movement against German occupation. As fighting against the Axis Powers devolved into a bitter civil war, Mihailovic turned against communist guerrillas led by Josip Broz Tito.
With the conflict raging, some Chetnik forces hunted and killed not only their ideological opponents but also Croats, Bosnian Muslims, and others on Yugoslav territory. Historians say tens of thousands were slain by the Chetniks because of their ethnicity.
In 1946, with Josip Broz Tito at the helm of postwar Yugoslavia, Mihailovic was captured and tried. He was found guilty of war crimes, collaborating with the Axis Powers, and agreeing a cease-fire with the Nazis.
But he was also posthumously awarded the Legion of Merit in 1948 by U.S. President Harry Truman for his role in rescuing hundreds of U.S. airmen downed by the Axis Powers over Serbia.
As Yugoslavia unraveled in war in the 1990s, the Chetnik movement underwent a revival. The name, insignia, and trademark beards were adopted by some Serbian paramilitaries as they fought to carve out more room for ethnic Serbs.
'Religious Hatred And Intolerance'
Mihailovic’s conviction stood until May 2015, when the Higher Court of Belgrade ruled that the verdict was now "null and void."
"The Chetnik celebration is an open attempt not only to deny history but also to forge a new one," Branko Todorovic, president of the Helsinki Committee for Human Rights in Republika Srpska, the Serb entity in Bosnia, told RFE/RL’s Balkan Service.
Bosnian Prime Minister Denis Zvizdic quickly denounced what he called the "spread of national and religious hatred and intolerance" and the intimidation of Bosnian Muslims.
The European Union's ambassador to Bosnia, Lars-Gunnar Wigemark, also condemned the event, while the United States said it was "appalled" by it.
"Such behavior is unacceptable. We expect the relevant authorities to take the necessary steps to address these threats and hold accountable those responsible," the Embassy in Sarajevo said in a tweet.
The annual gathering, organized by an association called the Ravna Gora Chetnik movement, the name by which Mihailovic’s Chetniks were known, has made headlines in the past.
In 2016, a journalist with N1 TV was assaulted during the event.