This article traces how Polish national activists in the Borderland Guard (Straż Kresowa) constructed the local boundaries of the nation in the multiethnic borderland of Polish-occupied Volhynia. In 1919 and 1920, as Russian imperial structures collapsed and those of the Polish state remained embryonic, these men created a series of exclusions and conditional inclusions that emerged from, rather than in spite of, their nominal celebration of democracy and equality. In addition to debating how far—and on what terms—Ukrainians (or Ruthenians) and Jews could be included in the Polish nation, they also marked out internal Polish boundaries, based on religious, linguistic, economic, class, and affective criteria. Taking readers beyond intellectual debates in Warsaw and toward competitive local questions about the grounds for national membership, the article challenges the usefulness of the broader analytical dichotomy between the “inclusive” (civic) and “exclusive” (ethnic) strains of modern nationalism.