In the third episode of this landmark series charting the story of human civilisation, Andrew Marr plunges into the spiritual revolutions that shook the world between 300 BC and 700 AD.
This was an age that saw the bloody prince Ashoka turn to Buddhism in India; the ill-fated union of Julius Caesar and Egypt's Cleopatra; the unstoppable rise of Christianity across the Roman Empire and the dramatic spread of Islam from Spain to Central Asia.
Each dramatic story pits the might of kings and rulers against the power of faith. But Andrew Marr discovers that the most potent human force on the planet came from the combination of faith and military power. Both Christianity and Islam created new empires of 'the word and the sword'.