In part because of the Serbian government’s frequent criticism of Brussels, the prospect of membership in the European Union is losing public support in Serbia. An opinion survey by the European Union Integration Office in Serbia in July found 49 percent of Serbians favoring membership — a drop from a high of 73 percent in 2009 — with the percentage opposed jumping from 12 to 27.

Observers also note the return of the political language of the 1990s by some senior Serbian government officials as they attack dissenters as traitors, spies and enemies. Mr. Vucic’s remarks about forgetting the past, they say, echo those of the Yugoslav leaders who told citizens to look to the future instead of addressing the World War II atrocities committed by Yugoslavs against other Yugoslavs. The residual hatreds and feelings of injustice left by the unpunished crimes of World War II helped fuel the ferocity of Yugoslavia’s civil wars in the 1990s.

A former Serbian general, Vladimir Lazarevic, served two-thirds of a 14-year sentence for crimes against humanity for his role commanding the Yugoslav military in the forced deportations of more than 700,000 ethnic Albanians in Kosovo.

After being released from The Hague in 2015, General Lazarevic received a hero’s welcome at the Serbian airport, where he was met by two government ministers, the head of the Serbian military and other senior officials. Last month, he gave a lecture to cadets at the military academy in Belgrade.

The title of the lecture: “The heroism and humanity of Serbian soldiers in their defense against the NATO aggression.”

The European Union warned against letting a war criminal give a lecture to the academy, but the general received high praise from the defense minister, Mr. Vulin, a former close political ally of Mr. Milosevic’s widow, Mirjana Markovic. Mr. Vulin told a group of veterans last month that Serbia no longer needed to feel shame over officers like General Lazarevic.

The public support for a war criminal appalled human rights activists and Western officials.

“We expect political leaders to honor the victims of the past conflicts and sincerely promote reconciliation in the Western Balkans,” Maja Koncijancic, a spokeswoman for the European Union, said in a statement.