Abstract This study examines the Greek Army’s role in shaping domestic politics during the modern history of Greece (1821–1949), highlighting its dual function as both a stabilizing force and an agent of political intervention. Through an analysis of key historical episodes, including the Goudi Coup (1909), the National Schism (1915–1922), and the interwar coups, the research explores how the army influenced governance, national unity, and state-building. The Greek Army’s relationship with the monarchy is also scrutinized, from its role in consolidating King Otto’s rule to its pivotal involvement in restoring and later undermining King George II. The study employs an interdisciplinary approach, drawing on military archives, political memoirs, and secondary literature, to reveal how class, regional, and ideological divisions within the army mirrored broader societal tensions. Particular attention is given to the National Schism’s long-term effects on military cohesion and its impact on the Greek Civil War (1946–1949). This research argues that the Greek Army was central to the nation-building process, yet its entanglement in domestic politics often destabilized democratic institutions. By situating the Greek Army within comparative and transnational contexts, this study contributes to broader discussions on the political role of militaries in emerging nation-states. Keywords: Greek Army, Modern Greek History, Domestic Politics, Nation-Building, National Schism, Military and Monarchy