This book examines major foreign conflicts from the Spanish-American War through Vietnam, arguing that international conflicts have strong effects on American political parties, elections, state development, and policymaking. First, major wars expose and highlight problems requiring governmental solutions or necessitating emergency action. Second, despite well-known curtailments of civil liberties, wars often enhance democracy by drawing attention to the contributions of previously marginalized groups and facilitating the extension of fuller citizenship rights to them. Finally, wars affect the party system. Foreign conflicts create crises – many of which are unanticipated – that require immediate attention, supplant prior issues on the policy agenda, and engender shifts in party ideology. These new issues and redefinitions of party ideology frequently influence elections by shaping both elite and mass behavior.