Through the life story of a sailor, merchant, former prisoner, and soldier, this article explores the Brazilian postcolonial empire’s experiments in settlement and domestic colonization during the Age of Revolutions. Johann Heinrich Lembke’s journey—from incarceration in the German territory of Mecklenburg-Schwerin, to his conscription into the Brazilian armed forces, to his eventual desertion—offers a unique entry point into the sociopolitical mechanisms of empire-building in the New World. Drawing on records from German, British, Portuguese, and Brazilian archives, this article traces Lembke’s trajectory within broader processes of territorial expansion, settler-military strategies, and normative pluralities that shaped imperial governance in Latin America. It illuminates the porous continuum between penal, military, and settler colonization projects, illustrating how such systems functioned as overlapping mechanisms of governance and control. Methodologically, a microhistorical analysis links the European and South American contexts, as this research uncovers the experimental nature of Brazil’s border policies and challenges binary representations of settlers in the South America. Lembke’s case thus becomes a window onto Brazil’s imperial formation, revealing how ordinary actors navigated the ambiguities of empire-building.