Overview:September 2016: Stacey Dooley embeds herself on the frontline with the extraordinary all-female Yazidi battalion, who are fuelled to take revenge against the so-called Islamic State. As the battle to take Mosul from ISIS advances in Northern Iraq, in this extraordinary film for BBC Three, Stacey finds these young women's lives have been transformed by a desire to avenge their loved ones who were murdered by Isis.