Terrorism and Ivory Towers (EN)

The EU is under attack: from below. New terrorist attacks in Vienna and Nice have opened a long-sealed scar of the past attacks during the Christmas time in Germany or of the shootings in France. It seems like the enemy of terrorism is lurking behind corners, walking in the shadows and nobody knows when or where is it going to hit next. Why is this? What is the main reason and who is the main offender? Is there any way to resolve this issue peacefully? Or have we lost all hope?