On 23 September 2002, European Union leaders reached agreement to proceed with an eastward enlargement that would incorporate multiple Central and Eastern European countries into the bloc. The decision formalized accession negotiations and timelines for a cohort of nations that had been undergoing transition from communist rule since the late 1980s and early 1990s. This vote in 2002 followed years of political, economic and legal reforms driven both by candidate countries and by EU accession criteria known as the Copenhagen criteria. Background After the Cold War, former communist states in Central and Eastern Europe sought closer ties with Western Europe. The European Union, seeking to stabilize the continent, contain potential conflicts and extend its single market, opened membership discussions with multiple applicants. Accession required candidates to demonstrate stable democratic institutions, market economies, and the adoption of the EU acquis — the body of common rights and obligations binding all member states. Negotiations and decision By 2002, formal negotiations were well advanced with a group of countries that included Poland, Hungary, the Czech Republic, Slovakia, Slovenia, Estonia, Latvia, Lithuania, Malta and Cyprus. The vote on 23 September 2002 by EU leaders committed the Union to admitting these candidates once they completed outstanding reforms and fulfilled negotiated provisions. The agreement laid out transitional arrangements on matters such as agricultural policy, regional funding and labor mobility, and set an accession date framework that ultimately led to the enlargement on 1 May 2004. Scope and significance The 2002 decision was significant for its scale: it set the stage for the largest single expansion of the EU by number of states and population since its founding. It integrated many countries that had been within the Soviet sphere of influence, reshaping the geopolitical map of Europe. Economically, enlargement expanded the EU market and created opportunities and challenges for structural funds, budgetary allocations and regulatory alignment. Politically, it strengthened EU institutions by increasing membership diversity and prompted internal debates over decision‑making, enlargement fatigue and future reform of EU governance. Implementation and aftermath Following the 23 September vote, candidate countries continued to adopt and implement EU laws and standards. Remaining technical and legal benchmarks were cleared through treaty ratifications and domestic reforms in the lead‑up to accession on 1 May 2004 for ten countries. The enlargement required coordination on transitional measures, in particular for labor mobility and sectoral policies, and prompted some existing member states to apply temporary restrictions on workforce access from new members. Over the longer term, the enlargement contributed to deeper integration in areas such as trade and regulatory alignment while also exposing the EU to new internal political dynamics and policy priorities. Historical assessment Historians and policy analysts view the 2002 decision as a turning point in post‑Cold War European integration: it consolidated democratic transitions in candidate countries and extended EU norms and markets across a much larger geographic area. At the same time, scholars note that enlargement produced long‑term governance and budgetary challenges for the EU and ignited debates about institutional reform, cohesion policy and the bloc’s strategic orientation. The vote on 23 September 2002 therefore stands as both a culmination of a decade of eastward outreach and the starting point for managing integration of a markedly larger and more diverse union.