The Austrian colonel, in the field-green uniform worn for formal occasions, was not amused, and had no hesitation in saying so.

“It’s not right,” Col. Erwin Fitz said. “It’s a circus.”

The 59-year-old officer, an army historian, had come to pay his respects on Saturday at the Sarajevo street corner where Archduke Franz Ferdinand and his wife, Sophie, were assassinated on June 28, 1914, providing the impetus for the collapse of the fragile European order of the time and the outbreak of World War I.

What unsettled the colonel were shenanigans, deeply disrespectful as he saw it, involving a lineup of joyful, laughing people clambering into the back seat of a mock-up of the open-topped car in which the aristocrats died. The car, built from an old Land Rover by a Sarajevo motoring enthusiast and his 15-year-old son, was part of the carnival that some in Bosnia’s capital made of the centenary on a blazing hot Saturday similar to the day of the assassinations.

For others in this city of 300,000, the centenary was a more somber occasion. While the bells of the Roman Catholic cathedral pealed across the city at noon to mark the hour of the assassinations — strictly speaking, about an hour after the fatal shots were fired — preparations were underway at the rebuilt City Hall for a concert at sunset by the Vienna Philharmonic Orchestra, the centerpiece of commemorations that have been mainly organized, and paid for, by the European Union.

Still, there was much about Sarajevo, which bears the scars of three wars in the past century — World Wars I and II and the sectarian fighting of the early 1990s, in which 11,500 Sarajevans died — that spoke for a less reflective mood. Especially for the young, the 100-year anniversary of the assassinations seemed more of a pageant than a moment to ponder what in the human spirit, or the tangled concert of nations in 1914, had led to a war that cost as many as 20 million lives by the time it ended in 1918, by some historical estimates.

Outside the museum — at the time a grocery store and delicatessen — that stands at the corner where the assassin fired his fatal shots, a teenager in a facsimile of the uniform then worn by the archduke was posing in a vehicle made up to resemble the Gräf & Stift open-topped limousine that carried the couple. The boy, Emir Kapitanovic, 15, was the son of the car’s owner, and sat beside a broad-brimmed hat and crinoline veil of the kind worn by Sophie, Duchess of Hohenberg, when she was shot, offering them as dress-up items to a crowd of women and young girls eager to be photographed beside him in the car.

The assassin, a Bosnian Serb named Gavrilo Princip, was a Yugoslav nationalist who killed the couple, heirs to the Austro-Hungarian Empire, in the hope of liberating Yugoslavia from foreign rule.

After World War II, Yugoslavia officially honored Princip for having struck a blow that led to the breakup of the empire and Bosnia’s reincarnation as part of Yugoslavia. The place where he stood to fire the shots was marked by embossed footprints. The footprints are gone now; the concrete paving stone that bore them now exhibited inside the museum, part of a revision in recent years meant to eliminate all elements of Princip hagiography and leave it to visitors to decide whether he was a liberator, an anarchist killer or a terrorist motivated by sectarian and ethnic hatreds, all views that have been embraced in the deeply fractured Bosnia that emerged from the war of the 1990s.

Colonel Fitz, the Austrian officer, had begun his day with a commemoration in the Lion Cemetery on a hillside above the city, where 2,254 Austrian soldiers killed in Bosnia in World War I are buried. The colonel said the ceremony, beneath a large statue of a lion that is one of the many Austro-Hungarian relics in the city, had involved an Austrian military band, and ambassadors and military attachés from nations that were allied with the Austro-Hungarian Empire after it responded to the Sarajevo assassinations by declaring war on Serbia in July 1914.

The colonel noted quietly, and without recrimination, that none of the ambassadors were from the countries that now share common membership in the European Union with Austria, but were the enemies of Austria and its main ally, Germany, in World War I. Those old alliances have been a ghostly presence in the current commemorations, with nations that have long since made an official bonfire of the nationalist furies that impelled the 1914-18 war, and the Second World War in 1939-45, taking carefully calibrated roles in Sarajevo.

An academic conference to debate the causes and consequences of the war became eerily anodyne when scholars from France, Germany, Bosnia, Serbia and Croatia and other European nations fell into a dispute ahead of the gathering about the topics to be discussed and the speakers who would address them. In the end, the program for the conference, held at the Hotel Hollywood in the mainly Serbian town of Ilidza, where the archduke and his wife spent their last night before taking a brief train ride into Sarajevo, was devised to avoid any open disputes about the role of Princip or other issues touching on war guilt.

The compromise was guided by the European Union and its diplomatic mission here, which tries to draw rival Bosnian sectarian groups into a less wary and abrasive posture on Bosnia’s future than the main protagonists among the Serbs, Croats and Muslims have shown since the United States-sponsored Dayton agreement that ended the sectarian killing of the 1990s. Peter Sorensen, a Danish diplomat who is the European special representative to Bosnia and Herzegovina, describes his role as that of a referee overseeing a “fierce fight, on a daily basis, over maintaining the political space” allotted to the groups under the Dayton pact.

But Mr. Sorensen and other European diplomats failed to persuade the Bosnian Serb political leaders to join in shared commemorations of the centenary of the Sarajevo assassinations. Instead, Milorad Dodik, the most militant of the Bosnian Serb leaders, led his followers on Friday in erecting a seven-foot statue to Princip in a hardscrabble park in Lukavica, a suburb of Sarajevo and a Serbian military stronghold during the fighting of the 1990s. On Saturday, Bosnian Serbs held more celebrations of Princip and his fellow conspirators in Visegrad, 70 miles southeast of Sarajevo, where they also re-enacted the assassination.