During the 1990s , the conflicts in the Balkans gave impetus to developing the EU 's Common Foreign and Security Policy ( CFSP ) . The EU failed to react during the beginning of the conflict , and UN peacekeepers from the Netherlands failed to prevent the Srebrenica massacre ( July 1995 ) in Bosnia and Herzegovina , the largest mass murder in Europe since the Second World War . The North Atlantic Treaty Organization ( NATO ) finally had to intervene in the war , forcing the combatants to the negotiation table . The early foreign policy experience of the EU led to foreign policy being emphasised in the Treaty of Amsterdam ( which created the High Representative )
Srebrenica massacre
Srebrenica massacre
History of the European Union