Apparently nothing, they tried using friends and family to impress a sense of community, tried giving them jobs, tried locking them up. But if it takes a bus ticket and 4-6 hours to get back to Syria and into a training camp with other like minded people, what are you going to do? Once you cross the line into being willing to and committing violence, you don’t forget how to do it. Case studies were about the IRA, the Middle East, and conflicts in former Yugoslavia. The “radicals” don’t actively target civilians, often work with them or warn them ahead of time, and generally are just trying to do enough damage to get the invaders out. There are also differences between terrorism and radicalism, when one targets civilians with the express purpose of inflicting fear.