WHAT a difference a year makes. After a long period of improvement Serbian-Croatian relations have plummeted to old lows. In 2011 Ivo Josipović, Croatia’s president and Boris Tadić, his Serbian counterpart, were spending so much time together that questions began to be asked about quite why they were seeing one another so much. Now the leaders of Croatia and Serbia avoid each other as much as they can.

Relations between Croatia and Serbia started to cool when Tomislav Nikolić, a former extreme nationalist, became president of Serbia last May and cooled further when Ivica Dačić, the former spokesman of Slobodan Milosević, the wartime of leader of Serbia, became prime minister last July.  During the Yugoslav wars Mr Nikolić was a member of the extreme nationalist Serbian Radical Party, which aimed to create a Greater Serbia in Bosnia and Croatia. In May, Mr Nikolić told a German newspaper that Croats should not return to live in Vukovar, the town in Croatia that Serbian and Yugoslav army artillery had reduced to rubble in 1991, because it was a Serbian town. Since then Mr Josipović has not met with Mr Nikolić.

On November 16th the United Nation’s Yugoslav war crimes tribunal acquitted two Croatian generals of war crimes against Serbs. This has provoked another, more severe chill in relations. Ante Gotovina and Mladen Markač (pictured above) were convicted in 2011 but their successful appeal means that no Croats have been convicted by the UN tribunal of any crimes against Serbs in Croatia during the war years. The acquittal also means that the tribunal has judged that there was no “joint criminal enterprise” designed to drive out some 200,000 Serbs from the Krajina region in 1995.

In the early 1990s Serbs in Croatia declared a breakaway state on one third of Croatian territory. They were backed by arms from Serbia and the Yugoslav Army. Croats fled or were ethnically cleansed from this territory. When the Croatian army retook most of the territory in the Krajina region in 1995 almost all the inhabitants fled, or were ethnically cleansed, few to return.

The acquittal has been greeted ecstatically in Croatia. It was met with anger in Serbia, even amongst liberals and human rights campaigners such as Nataša Kandić . Now however Mr Nikolić has decided to ramp up the issue. In an interview with the daily Kurir he said that while he had come to power intending to establish good relations with Croatia and Bosnia, “this thing with Croatia is not going well”. He then attacked Croatia because the anniversary of the attack on Krajina, called Operation Storm (which for Croats meant the liberation of the territory held by Serbs backed by Serbia) is a national holiday on which, he said, the country “celebrates its crime”. Then he added:

“Up until this verdict, the president of Croatia looked for reasons not to reconcile. All the stories that he is angry because I said something about Vukovar are lies. He was waiting for this verdict. Now he would like to talk – I, as the president of a people who had committed crimes and he as the president of a people have not been convicted of anything.

 Croatians know that the crime that was committed in Storm was atrocious, that it will nag them as long as they live, but they are celebrating that no one has been punished for it.”

 Mr Josipović replied that he could not believe that such statements “were being made “by a politician at the head of a country which wishes to be European”, adding that such statements “do not contribute to god relations and reconciliation”. Croatia would “not succumb to such hysteria.”

Vuk Jeremić, who was foreign minister under Mr Tadić, and who even then sparred with the Croats, quickly weighed into the fray. He is now president of the UN General Assembly. He embarked on a mutual exchange of insults with Mr Gotovina’s lawyer on twitter and has proposed a General Assembly debate on ad hoc UN war crimes tribunals next year, by a strange coincidence on the anniversary of the founding of the Croatian quisling state in 1941. At this debate, says the Serbian newspaper Večernje novosti, Mr Nikolić plans to “present a chronology of Serbian-Croatian relations since 1941.” Mr Nikolić says he will speak like Fidel Castro, “until they drive me out of the chamber.”

On November 29th the war crimes tribunal acquitted Ramush Haradinaj, a former Kosovo prime minister, for the second time of murdering and torturing Serbs, Albanians and others in 1998. The verdict was issued in the UN court's first ever retrial, which was ordered after appeals judges overturned the 2008 acquittals of Mr Haradinaj because of alleged serious intimidation of prosecution witnesses. The acquittal added to Serbia's anger and its conviction that the tribunal is only a kangaroo court designed to single out Serbs as war criminals.

Oliver Antic, an advisor to Mr Nikolić blamed Germany for what he sees as international ostracism of the Serbs and favourable treatment of Croats. Germany had, he said, “welcomed its faithful allies from the second world war, while rejecting the rest”. Germany has been exasperated with Serbia for some years over its Kosovo policy. Barring any last minute hitch, Croatia will join the EU next year while Serbia remains firmly on the waiting list. In the past Croatian leaders have said they would not use their position inside the EU to impede the EU accession of any of its neighbours, in the way Slovenia has done for Croatia, but in such an atmosphere, all bets are off.

In spite of all this economic links are being consolidated between the two countries. Both the Serbian and Croatian ambassadors to London attended an event on November 28th to mark a €307m ($399m) financing package to Atlantic Grupa, a Croatian company, by the European Bank for Reconstruction and Development. Atlantic Grupa is heavily invested in Serbia, and the rest of the former Yugoslavia and now aims to expand significantly in Russia and the CIS countries.