A comment about ISIS at Jerry Pournelle's site:
ISIS has more to offer its soldiers than the Western militaries do:I'm going to guess that their soldiers are not subject to divorce-rape the way Western soldiers are either. The fact that they are willing to pay for children born to ISIS couples is an ominous sign that they are planning for the future.
Arab men in traditional culture have NO contact with women at all, not even dating, until they’re married. That can often not be until one reaches the thirties. This has the results you would expect.
ISIS, by contrast, offers a quick marriage both to male and female recruits. For the men the attractions of marriage are obvious. Women are offered "wonderful husband and a free house with top-of-the-line appliances, such as a fridge, microwave and even a milkshake machine". Moreover, ISIS will pay a stipend for every child the couple bears.
Framed that way, it’s obvious why they exert such a powerful draw. People who aren’t ever going to amount to much , people who have been let down by their traditional culture, are flocking to a place that offers them a fresh start. And sex , of course.