This BBC podcast is supported by ads outside the UK.
That's how we deliver reliable energy to millions across the world.
Aramco, an integrated energy and chemicals company.
Learn more about us at aramco.com.
Today's episode is sponsored by Smart Travel, a podcast from NerdWallet.
Do you have a friend who treats airfare like a puzzle and somehow always ends up with a first-class upgrade?
Smart Travel is like that friend, minus the group texts.
NerdWallet's travel journalists break down the pros and cons of travel decisions,
like when lounge access is worth paying for and which hotel loyalty programs actually pay off.
Make your travel dollars work harder.
Follow Smart Travel on your favourite podcast app.
This program contains descriptions of violence, injury and death in war zones,
which some listeners may find distressing.
I'm watching a video of a man in army uniform with a gun running towards gunfire.
However, this man, despite his appearance, is not a soldier.
He's a Christian missionary.
This is 4 May 2017, right outside of northwest Mosul.
People fleeing, ISIS shooting at him.
You're listening to the documentary from the BBC World Service.
I'm Rajiv Gupta, and for Heart and Soul, I'm speaking with David Eubank,