David Bergen : More and more terrorist and insurgent groups are swearing loyalty to IS . , one of which was al Qaeda in Iraq , the parent organization of ISIS that has now split off from the core al Qaeda organization . In past six months , IS has recruited about a dozen groups , he says . IS ' perceived success is attracting these groups , Bergen says .
David Bergen : More and more terrorist and insurgent groups are swearing loyalty to IS . In past six months , IS has recruited about a dozen groups , he says . IS ' perceived success is attracting these groups , Bergen says .