2002 13th December
Copenhagen Enlargement Agreement
Supports the agreement completing accession negotiations with ten countries scheduled to join the Union in 2004.
European integration · permanent subject timeline
European Union Enlargement, 2004
The largest single expansion in the history of European integration. This page combines historical context with 15 matching records drawn directly from the World History Database EEC archive.
Historical context
European Union Enlargement, 2004: overview and significance
What happened?
Ten countries joined the European Union on 1 May 2004 after a long process of accession negotiations and institutional preparation.
Why was it important?
The 2004 enlargement reunited much of post-Cold-War Europe within one political and economic framework and increased membership to twenty-five states.
World History Database records
European Union Enlargement, 2004 timeline
The records below are selected from the 936-record EEC and European integration archive and rendered as static HTML in chronological order.
2002
2002 13th December
Copenhagen Enlargement Agreement
Supports completion of accession negotiations with ten countries scheduled to join the Union in 2004.
2002 13th December
Copenhagen Enlargement Agreement
Supports completion of accession negotiations with ten countries scheduled to join in 2004.
2003
2003 1st January
Fourth Greek EU Presidency
Papandreou steers foreign-policy work during the 2003 Greek Presidency, including enlargement and Western Balkan priorities.
2003 1st January
Fourth Greek EU Presidency
Begins Greece's fourth rotating Council Presidency with enlargement and Balkan integration among its priorities.
2003 1st February
Treaty of Nice Enters into Force
The Nice Treaty becomes legally effective during Ahern's government, preparing Union institutions for enlargement.
2003 1st February
Treaty of Nice Enters into Force
The Nice Treaty becomes legally effective during Berlusconi's government, completing institutional reforms designed for enlargement.
2003 16th April
Athens Enlargement Treaty Ceremony
Participates as ten accession countries sign their treaties during the Greek Presidency.
2003 1st July
Italian EU Council Presidency
Begins Italy's rotating Council Presidency with treaty reform and enlargement among its priorities.
2004
2004 1st January
Sixth Irish EU Presidency
Begins Ireland's sixth Council Presidency with enlargement and constitutional negotiations as central priorities.
2004 1st May
Eastern Enlargement
Chirac welcomed ten new member states as the European Union completed its largest enlargement.
2004 1st May
European Union Enlargement
Heads the German government when ten new member states join the European Union in its largest enlargement.
2004 1st May
European Union Enlargement
Heads the Greek government when ten new member states join the European Union.
2004 1st May
Day of Welcomes
Hosts celebrations welcoming ten new countries during the largest enlargement in European Union history.
2004 1st May
European Union Enlargement
Heads the Italian government when ten new member states join the European Union.
Editorial provenance
Sources and editorial review
Compiled and edited by World History Database.
Historical context is editorial material; the chronology is generated from World History Database EEC records.
Last reviewed: September 2026.
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