An unprecedented look inside the war against violent extremism, beginning with a look at the US and Iraqi forces' battle to regain control of eastern Mosul.

As the battle for Western Mosul begins, a unit prepares to deploy to Afghanistan. Young people leave the Caribbean island of Trinidad to fight for ISIS.

While the battle for Mosul rages in Iraq, American and Colombian agents fight to prevent ISIS from reaching US shores.

The battle for Mosul may be nearly won, but ISIS's ideology spreads. They recruit fighters from far and wide, including Trinidad and Tobago.

While US marines assist the Afghan National Army, The Pentagon tries to crack down on extremist threats across the globe. Special operations forces head to Africa. (S1, ep 6)