The study is based on the thesis that the members of Czech communities abroad who left their country before the period of the „National Awakening“ imbibed the national idea thanks to the „assistance to fellow countrymen“ in the interwar period. This was motivated by the effort to „save“ the communities of fellow countrymen from being assimilated into the majorite society of South-Eastern Europe. The following article aims to apply constructivist approach to nation into the study of the phenomenon of fellow countrymen. Ethnicity only comes to the foreground of the organizing criteria of these collective entities after the arrival of assistants. The first part of the study presents the organizing mechanism of sending the assistants on the example of the Bulgarian community Gorna Mitropolia. The other part represents an effort to conceptualize in a broader way the constructivist approach. The communication network of the state and the foreign out-migration therefore rested on the mission-evangelizing basis. The communities involved accepted, besides the already existing territorial and linguistic identification, also another aspect of the collective identity – the identification with the shared past. Only after the application of the „ethnic diction“ that stressed the common origin we can consider the Protestant groups abroad as ethnic communities of Czech fellow countrymen.