The book analyses how political parties compete and strategise on the issue of territorial reform using case-studies that include countries from both Western (Belgium, Germany, Italy and Spain) and Central-Eastern Europe (Poland, Slovakia and Romania). Each case-study considers different drivers of decentralization, such as territorial identities and the demands of regionalist parties for territorial autonomy or independence, efficiency concerns related to issues of uneven economic development and economic competitiveness, the pressure from supra-national organizations (especially the EU), as well as different combinations of these drivers. They also consider how the ideology and organisation of state-wide parties and the institutional context in which they compete shape their responses to these drivers and their strategy towards the question of territorial reform. This collection investigates the logic of the actions that guide political parties’ strategy to highlight trends that are apparent across the case-studies. This book was originally published as a special issue of West European Politics.