European Enlargement between War and Fundamental Values: A Historical Perspective

Scholars debate what drives European Union (EU) enlargement. On one side of the debate are those who see such decisions as based on potential members’ progress on themes related to the Union’s core values. There are also those, especially lately, who highlight the role of geo-politics, focusing on the influence of Russia’s full-scale invasion of Ukraine as a driver of recent candidacy decisions. We build on this European integration literature to develop novel hypotheses testing these perspectives one against the other, and ask: What drives EU enlargement? By answering this question, we add to this debate by closely analysing trajectories of progress on EU core values leading to the EU’s decisions to grant candidacy status and membership. The analysis spans 26 countries and four enlargement waves spanning the years 1990 to 2023. We find that the EU’s decisions on candidacy depend on progress on certain fundamental values, specifically democracy and human rights, as well as geopolitical concerns related exclusively to the Russian full-scale invasion of Ukraine. Progress on rule of law, another fundamental value, is less critical to positive candidacy decisions. In comparison, decisions to grant EU membership seem to depend on progress on all aspects of fundamental values. Our findings support recent qualitative studies that have identified the structural change in the EU’s enlargement logic as a result of Russia’s full-scale invasion of Ukraine, contributing to the ongoing debate about the drivers of EU enlargement. In so doing, our work places the most recent enlargement decisions into a longer historical context and considers the newer attention on geopolitics in the process of enlargement.