Following the terrorist attacks of September 2001 in the USA and those in Madrid in March 2004 and in London in July 2005, EU Member States stepped up their cooperation in the fight against terrorism.
Tar éis ionsaithe sceimhleacha Mheán Fómhair 2001 i Stáit Aontaithe Mheiriceá agus na hionsaithe a rinneadh 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.