David,

In your estimation, how much of this is the direct appeal of jihad or Islamism, and how much of it is the appeal of adventure, etc for young men? The 20th century alone is replete with young men joining foreign causes (IDF, French Foreign Legion, Spanish Civil War, South Africa, Nazi SS, etc). It seems to me like there are many who went abroad looking for that kind of experience, only to become disillusioned either with war, ISIS, or some combination in between. What are your thoughts?