INTRODUCTION

Much like across the rest of Europe, the vote by the British people to leave the European Union was not expected by the countries of south-eastern Europe. Amongst the newest members of the EU, they had all striven to become members of an organization that, along with NATO, had come to define European politics. This amplified the shock that the United Kingdom, a leading European state that had backed the enlargement of both organizations, had now decided to turn its back on the EU. Geographically, Bulgaria, Croatia, Romania and Slovenia are part of a wider region in which geopolitics and history did not facilitate or encourage regional cooperation until quite recently. Before fulfilling their post-Cold-War strategic priorities – EU and NATO membership – the four countries had supported regional cooperation formats or initiatives only when they were sure the respective format would promote their accession agendas to the EU rather than delay them. Geographically, some of them are parts of other regions – the Danube (Bulgaria, Croatia and Romania), the Black Sea (Bulgaria and Romania) and the Mediterranean (Croatia and Slovenia). Despite this, and while not constituting a formalized format, the four countries covered here as south-eastern Europe have common interests that form the backdrop for understanding their approach to the UK’s renegotiation, and especially their common concerns about the outcome of the June 2016 referendum. They share common interests over the future terms of relations between the EU and the UK, as well as with regard to the future of the EU without the UK. Not belonging to the heavyweights in the EU, all four countries are interested in pursuing a common European position in the negotiations with the UK and did not join with those opposed to entrusting the negotiations to the European Commission.

Because of the UK’s strong strategic role with regard to security matters, bilateral relations between the four countries of south-eastern Europe and the UK have been much more important in terms of support for EU and NATO enlargement than in terms of economic and trade cooperation.