For centuries, armed conflicts were fought by armies on vast battlefields. Even if cities were besieged or sacked, fighting rarely took place in the streets.
In the 21st century, wars are being fought in cities.
From 2010 to 2015, half of the civilians who were killed in armed conflict died in Iraq, Syria, and Yemen.
And 70 per cent of these people lived in cities.
Almost nowhere is worse affected than the Iraqi city of Mosul.