When Napoleon defeated Venice in 1797 found that Istria was populated by Italians on the coast and in the main cities , but the interior was populated mainly by Croats and Slovenians : this dual ethnicity in the same peninsula created a situation of antagonism between Slavs and Italians for the supremacy of Istria , when started the first nationalisms after Napoleon 's fall . When Napoleon defeated Venice in 1797 , he found that Istria was populated by Italians on the coast and in the main cities , but the interior was populated mainly by Croats and Slovenians : this dual ethnicity in the same peninsula created a situation of antagonism between Slavs and Italians for the supremacy of Istria , when started the first nationalisms after Napoleon 's fall .