By Nick Thorpe
BBC News, Kosovo
The recognition of Kosovo by Croatia, Hungary and Bulgaria comes at a crucial moment.
Protesters in Belgrade show their anger against Kosovo independence
Serbian diplomats and their Russian allies have tirelessly argued that the independence of Kosovo undermines the stability of the Balkans.
Those who back independence, led by the United States, Britain, Germany and France, argue that it serves stability; that the last loose piece of the Balkan jigsaw has now been pushed into place.
As Serbia's neighbours, Croatia, Hungary and Bulgaria have shown that they accept the latter argument.
"Ties between the countries in the region are of special importance and their lasting stability remains an irreplaceable factor of peace and security in Europe," the Croatian government said in a statement on Wednesday.
The first country to leave the old Yugoslavia, Slovenia, which will hold the presidency of the EU until July, was among the first countries to recognise independence.
Croatia, at war with Serbia in 1991-92 and again in 1995, has worked hard to repair ties with Serbia.
Trade has grown rapidly, and reached $1bn in 2007. But Zagreb preferred to risk Serbia's ire, than live comfortably and ignore Kosovo.
Croatian President Stipe Mesic, himself a former Yugoslav leader, even identified with Kosovo in his statements after Croatia's recognition of Kosovo was made public. He compared Pristina's need for international recognition today, with Zagreb's need for recognition in 1991.
Another important factor which may have influenced Croatia's step is the forthcoming Nato summit in Bucharest in April.
Croatia, along with Albania and Macedonia, is hoping to receive an invitation in the Romanian capital to join the military alliance.
The US, as Kosovo's most powerful backer, has been urging all countries to recognise Kosovo. Anyone who wants to please the US today must follow that line.
Fears in Budapest
Hungary's recognition of Kosovo was taken with a heavy heart. Some 280,000 ethnic Hungarians live in the northern Serbian province of Vojvodina.
They have been the target of isolated but persistent attacks over the years: mostly physical assault and abuse by young Serbs, displaced from their homes in Croatia, Bosnia and Kosovo by the conflicts of the 1990s.
And fears have been expressed in the past weeks in the Hungarian media that recognition of Kosovo by Budapest could spark more attacks.
With the influx of Serb refugees in Vojvodina has come a growing strength for the ultranationalist Serbian Radical Party.
One Radical Party deputy suggested in recent days that ethnic Hungarians in Vojvodina might again be targeted.
His comments were angrily rounded on by ethnic Hungarian leaders. But the real test for the Hungarian minority in Serbia has already passed.
In March 1999 Hungary joined Nato. Ten days later, Nato began bombing Serbia, using Hungarian facilities and airspace.
As ethnic Hungarians queued to enter air-raid shelters in Novi Sad and other Serbian cities, their Serb neighbours asked why they didn't "go home".
The ethnic Hungarians insisted that their first loyalty was to Serbia. Some 50 young ethnic Hungarian conscripts died in Yugoslav army uniforms, fighting for Belgrade on the battlefronts in Croatia and Kosovo.
Bulgaria's decision to recognise Kosovo is painful for Serbia in a different way. As a predominantly Christian Orthodox country, it has a long history of friendship with Belgrade.
The two countries are also co-operating with Russia, with new gas pipelines across their territories, which will help Russia consolidate its increasingly important role in energy supplies to the whole of Europe.
Apart from pleasing the US, Bulgaria's leaders may also have decided that Russian influence in the Balkans is growing alarmingly.
And as a Nato member, Sofia wants to show where its own, first loyalties lie.
There is a rather 19th Century feeling in the Balkans today - small countries, choosing allies carefully, in a strategic battle between the Great Powers.