Where have 400,000 Serbs and Yugoslavs from Croatia gone, Serbian President Aleksandar Vucic asked Croatian officials on Saturday, ahead of events marking the 24th anniversary of the Croatian military and police operation Storm.

Relations between Belgrade and Zagreb become tense every year in August when the operation whereby Croatia in 1995 won the war against the Yugoslav People’s Army (JNA) and local Serb rebels, is commemorated.

Croats consider the operation a legitimate action that liberated then occupied parts of the country while Serbians see it as an act of ethnic cleansing of their ethnic kin from Croatia.

Vucic asked Croatian authorities to explain how it was possible that of the 582,000 Serbs and 106,000 Yugoslavs in Croatia’s 1981 census, only 184,000 declared themselves as Serbs in 2011.

The Serbian president is confident that by 2021, there will be fewer than 150,000 Serbs left in Croatia.

“If you say that 100,000 have emigrated for economic reasons, what about the other 400,000? How will you explain that?” asked Vucic.

He reiterated that for Croatia the day of Operation Storm was “a day of joy” while for Serbia “it is one of the saddest days in the country’s modern history.”

“We must not be ashamed of our tears, we should respect others’ victims but unlike before, we must also respect our, Serb victims, talk about them and not downplay them,” Vucic told reporters in Belgrade.

Serbia-Croatia relations have been deteriorating in recent years, mainly because of opposite positions on Operation Storm and the plight of Serbs in Croatia, Independent Democratic Serb Party (SDSS) president Milorad Pupovac said this past Thursday, adding that it was necessary to conceive a policy of remembering all the victims which would enable people to live normally.

Pupovac, a Croatian MP, said Croatia-Serbia relations had been bad since 2011 and that, aside from different interpretations of Operation Storm, “a serious problem for Serbs in Croatia” was the absence of sentences for war crimes, persecutions, the destruction of villages, and the prevention of returns.

This year Operation Storm has also caused disputes in relations with Bosnia and Herzegovina after President Kolinda Grabar-Kitarovic said that it had saved Bosnia and Herzegovina’s northwestern Krajina region from genocide and that she would like the neighbouring country never to forget who gave it a hand in the most difficult times.

A former commander of the Bosniak Army of Bosnia and Herzegovina, Hamdija Abdic Tigar, dismissed Grabar-Kitarovic’s statement, claiming that it was Bosniak troops that had liberated parts of Croatia.

“The hell they saved us… We kept this region safe for them the whole time. What would have happened had we been defeated? Where would Croatia be today? Its border would be running along the Karlovac-Karlobag-Virovitica line,” said Abdic.

The 24th anniversary of Operation Storm will be marked on August 5 and as in previous years, the central commemoration will be held in Knin, the former stronghold of Croatian Serb rebels, and it will be attended by the highest state officials.

On August 5 Croatia also observes Victory Day, Homeland Thanksgiving Day and Croatian Veterans’ Day.