The Judas Gate by Jack Higgins

The Judas Gate (Sean Dillon) - Sean Dillon is in charge of finding out who is the leader of English Muslims fighting against the Allied forces in Afghanistan known only as Shamrock. Justin Talbot, aka Shamrock, is the grandson of the owner of Talbot Industries. He has used his position in the firm first to supply arms to the Afghanis and eventually fighting for Al Qaeda. His boss in the Al Qaeda organization has ordered him to eliminate Dillon and his crew.