Sylvia Poggioli Visits The Bosnian City Of Mostar, where Muslims and Croats are having trouble overcoming the animosity left over from the war. The distrust between them is making it difficult for the European Union to carry out an ambitious plan to reunify and rebuild the city. The E.U. project has been underway for two years. Mostar was the scene of prolonged and vicious fighting between Croats and Muslims for much of the war in Bosnia.