On the Bosnian side of the border, you use Croatian dinars to pay for a coffee. Ask a man in combat gear for directions, and he will probably be a member of the Croatian Defence Council (HVO), a Bosnian Croat force armed and supported by the Croatian authorities in Zagreb. Look around the cafes, small shops and petrol stations, and you will see the red, white and blue Croatian flag with its distinctive chequerboard symbol. Some local Croats, though citizens of Bosnia, own Croatian passports issued in the past year.
These towns and villages are part of a Croatian mini-state in Bosnia proclaimed last July under the name of Herzeg-Bosnia. The area is not officially part of Croatia, but it is in most respects quite indistinguishable from its mother republic. If there is a difference, it is that more fighters drive around in stolen vehicles than in most of Croatia itself. You are also more likely to run into members of the paramilitary wing of the Croatian Party of Rights (HOS), an ultra-rightist political movement inspired by a dream of a Greater Croatian state.
In short, Herzeg-Bosnia is the Croatian mirror image of the rebel state the Bosnian Serbs have set up in northern and eastern Bosnia. Franjo Tudjman, the Croatian President, has not discouraged what amounts to the Croatian annexation of this area. In fact, the Zagreb government includes officials from Croatian- ruled parts of Bosnia. At various stages in the past 18 months, Mr Tudjman has negotiated with the Serbs - supposedly his mortal enemies - to effect a Serb-Croat partition of Bosnia.
The Bosnian Croats tried to speed up this process last week by ordering all Muslim military units to submit to their control in areas assigned to the Croats under the Geneva peace plan proposed by Lord Owen and Cyrus Vance. The order came from Bosnia's own Defence Minister, Bozo Rajic, a Croat who has never bothered to visit Sarajevo. Like other Croats nominally loyal to Bosnia's government, he prefers to base himself in Mostar, the capital of Herzeg-Bosnia.
Bosnia's Muslims and Croats are united in a military alliance against the Serbs, but their relationship has been tense throughout the war. In some areas, such as Gradacac in northern Bosnia, they have fought side by side. In the south-west and centre, however, they have often been at each other's throats. When violence erupted in Prozor in central Bosnia last October, the Muslims accused the Croats of engaging in the 'ethnic cleansing' that Serbian forces have practised elsewhere in the republic. The latest Muslim-Croat battles have lasted almost two weeks, and an attempt by Lord Owen and Mr Vance to broker a ceasefire last Wednesday came to nothing.
'Vance and Owen said they were very surprised by this conflict,' said Bosnia's Muslim Foreign Minister, Haris Silajdzic. 'I emphasise the word conflict because this is not just a misunderstanding any more. It was a well- organised attack by HVO militant groups. Geneva is being used to make a state within a state, which is unacceptable for Bosnia-Herzegovina, regardless of who wants to do it.' For their part, the Croats accuse the Muslims not only of provoking the clashes but also (in language reminiscent of Serbian claims) of aiming to turn Bosnia into a Muslim-dominated state. Miro Lasic, a Croatian member of Bosnia's presidency, said last week that Muslims outnumbered Croats in the Bosnian diplomatic and consular service by 20 to one. Even in the old Yugoslavia, he said, the Serbs never increased their representation over the Croats to more than six to one.
If Western audiences are surprised by the Muslim-Croat clashes, it may be the fault of governments and analysts who, in public at least, have emphasised Serbian atrocities and expansionist policies in Bosnia to the virtual exclusion of all other issues. Abominable though those actions are, they deflect attention from the crucial question of whether either Serbs or Croats sincerely regard Bosnia's Muslims as an equal, separate nation.
Many see the Muslims as Slavs whose conversion to Islam under Ottoman rule means that they are somehow still Serbs or Croats to be returned to their respective folds. In this war, the Muslims are victims of Zagreb as well as Belgrade.