“Al Qaeda was probably involved in the March [11] 2004 attack on Madrid [Spain]‘s metro system as well, the largest terrorist attack in Europe since World War II. Bin Laden and [al Qaeda second-in-command Ayman al-] Zawahiri now routinely claim this as one of their ‘raids’ into the West and point to its impact on the Spanish election that followed as a role model for creating a backlash against Western intervention in the Islamic world.”
– Bruce Riedel, The Search for Al Qaeda, Page 131