Chain of Command

Chain of Command begins with a look at the efforts of U.S. and Iraqi forces to regain control of eastern Mosul - the front lines of the war on extremism.

The battle for western Mosul begins, a unit deploys for Afghanistan and the war against extremism stretches to the Caribbean island of Trinidad.

American officials search for dangerous migrants in Colombia; back home, husband and wife Marines prepare for deployment to Afghanistan.

While coalition forces in Iraq gain ground in Mosul, in Trinidad and Tobago, local Muslim leaders are the tip of the spear in the fight against ISIS.

U.S. Marines advise and assist the Afghan army against the Taliban, and one officer watches on Skype as his son is born back home.

Marines continue to work with local forces in Afghanistan, while the U.S. also looks to curb extremism across Africa as well as the jungles of Panama.

The U.S. looks to finish off ISIS in Syria, fight off corruption in Afghanistan and train local forces in Africa in the war against extremism.

As U.S. Marines get set to leave Afghanistan, reminders of the problems there continue. Meanwhile in Niger, Special Forces endure a tragic loss.