Following the terrorist attacks in the United States in September 2001, Madrid in March 2004 and London in July 2005, EU Member States stepped up their cooperation in the fight against terrorism.
Tar éis na n-ionsaithe sceimhlitheoireachta i Meán Fómhair 2001 sna Stáit Aontaithe, i Maidrid i mí an Mhárta 2004 agus i Londain i mí Iúil 2005, chuir Ballstáit an AE dlús lena gcomhoibriú sa chogadh in aghaidh na sceimhlitheoireachta.