Yemen's civil war is a stew of local and foreign interests, from Washington, Saudi Arabia to Iran. And the latest battle may cost the lives of hundreds of thousands of civilians, if not millions.
Child victims are used to justify the cause, while young soldiers further it.
Al-Qaeda and Islamic State have both encouraged would-be terrorists to use cars and trucks as weapons.
The final article of our series on the historical roots of Islamic State examines the role recent Western intervention in the Middle East played in the group's inexorable rise.