However, with the continuing arrival of immigrants and the post-war emergence of Brussels as a center of international politics, the relative position of Dutch continued to decline.[1][31][32][4][5] Simultaneously, as Brussels' urban area expanded,[33] a further number of Dutch-speaking municipalities in the Brussels periphery also became predominantly French-speaking.[7][34] This cultural imperialism phenomenon of expanding Francization, often imbued with a condescending attitude of some unilingual French-speaking communities towards Dutch — dubbed "oil slick" by its opponents[9][35][13] — is, together with the future of Brussels,[36] one of the most controversial topics in Belgian politics.[24][19]