Zagreb cheered and Belgrade wept on Tuesday as they marked the 20th anniversary of Operation Storm, which ended the war sparked by Croatia's proclamation of independence from ex-Yugoslavia and sparked an exodus of Croatian Serbs.
Croatia was due to start celebrating its "liberation" with a military parade later Tuesday, with some 3,000 soldiers and war veterans, some 300 vehicles and 30 aircraft in the capital Zagreb.
Another ceremony, attended by top officials, will be held on Wednesday in the town of Knin, a wartime rebel Serb stronghold that Croatian troops recaptured on August 5, 1995.
"Operation Storm was a turning point (in the conflict), a brilliant military operation, justified and legitimate," Croatian President Kolinda Grabar Kitarovic said in a speech at a promotion ceremony in the defence ministry, encouraging citizens to be "proud and dignified" during the festivities.
The Croatian army launched Operation Storm on August 4, 1995, and saw 130,000 troops recapture in an 84-hour offensive a region that had been in Serb hands since 1991.
Sources differ on the number of ethnic Serbs who were brutally killed in the offensive, with tolls ranging from 600 to 2,500.
More than 200,000 others fled Croatia during and after the operation, with their property looted, seized or burned down. Barely half of those who fled have since returned.
Operation Storm ushered the end to the war that in total claimed about 20,000 lives.
The four-year conflict was sparked by Croatia's proclamation of independence from the former Yugoslavia that was opposed by Belgrade-backed rebel Serbs.
While Croatia celebrates the anniversary as its Victory Day, Serbia has declared Wednesday an official day of mourning and brands the operation the worst instance of ethnic cleansing in Europe in recent history.
Also on Tuesday, Serbian Prime Minister Aleksandar Vucic was to attend an official commemoration set to be held in the northwestern Serbian town of Sremska Raca, where hundreds of thousands of refugees took shelter 20 years ago.
Speaking at another religious ceremony held to commemorate the victims of the war, Serbian President Tomislav Nikolic chided the celebrations in Croatia.
"These fools have turned your hearths into fire, celebrating your suffering as their victory," he said.
Two former Croatian generals -- Ante Gotovina and Mladen Markac -- were initially sentenced by a UN court to prison terms of 24 and 18 years respectively for war crimes committed against ethnic Serbs.
The verdict was overturned by an appeals court and the two were eventually released.
Ethnic Serbs are still Croatia's largest minority, accounting for 4.5 percent of the population of 4.2 million -- down from pre-war levels of 12 percent.