In 1998, Osama bin Laden and Ayman Zawahiri declared war on the US, outlining a philosophy of the clash of civilizations which legitimised attacks on the West - both soldiers and civilians.
In the US, a group of politicians, who were to become known as the Neocons, believed they too had a moral duty to change the world.
Both groups found their opportunity in the attacks of 9/11 and the invasions of Afghanistan and Iraq. But both were to see their dreams perish with the increasing human cost of these wars and the reality that ideologies without popular support cannot change the world.
This episode airs from Tuesday, September 13, at the following times GMT: Tuesday: 2000; Wednesday: 1200; Thursday: 0100; Friday: 0600; Saturday: 2000; Sunday: 1200; Monday: 0100; Tuesday: 0600.