For more than 30 years, a top secret US special operations intelligence unit known only as “the Activity,” or more recently Task Force Orange, has operated in the shadows, tracking down America’s enemies around the world for Delta or SEAL Team Six to kill or capture, or more recently for Reaper drones to assassinate from afar. In an excerpt from the brand new eBook of his history of the Activity, “Killer Elite,” Michael Smith describes its role in the fight against Islamic State in Syria, Libya and Iraq.

The killing of Abu Musab al-Zarqawi in 2006 had caused extensive damage to al-Qa’eda in Iraq. It changed its name to Islamic State in Iraq but the surge in US troops and the successful recruitment of Sunni sheikhs to help counter the insurgency resulted in the Activity, Delta and their British SAS allies hunting down and killing most of the group’s leadership. When Abu Bakr al-Baghdadi took over in 2010, he moved it to Syria to regroup and, after the civil war broke out in 2011, absorbed all of the Syrian al-Qa’eda affiliates, claiming to have the backing of new al-Qa’eda leader Ayman al-Zawahiri.