The nationalization campaign promoted during the Estado Novo (1937-1945) interfered in the daily lives of immigrants and their descendents in Brazil - labeled as aliens because of the prevailing ethnicities and the differentiated cultures - requiring their assimilation (as a synonym for miscegenation) in the name of national unity. This study focuses on aspects of the military discourse related to this campaign and its objectives of forced assimilation, based on documents produced by Army officers working as agents for nationalization in the Itajaí Valley, in the State of Santa Catarina, a region viewed as a paradigm of "encystment", straying from the principles of "Brazilianness". It seeks to demonstrate how - in the campaign by the military - a concept of nation-state prevailed which denied legitimacy to any form of ethnic belonging, in accordance with the very parameters of Brazilian nationalist ideology as fomented since the 19th century.