The work examines the causes and consequences of the decline of classical Greek civilization, emphasizing endemic warfare among autonomous city-states as a central structural flaw. It surveys recurrent interstate and colonial conflicts, the rise of hegemonic powers, external invasions and internal factionalism, and the transformation of military, political and economic institutions that weakened civic autonomy. Attention is given to naval logistics, recruitment and funding, shifting alliances, and how prolonged violence and municipal fragmentation opened the way to external domination and the loss of independence. The account combines chronological narrative of major campaigns with analysis of underlying social and constitutional factors driving systemic collapse.