The US and Israel launched a joint military operation against Iran on Saturday, killing Iran’s supreme leader, Ayatollah Ali Khamenei. Why did Trump decide (again) to attack Iran during negotiations on a nuclear deal with the Islamic Republic? How does he sell a new war in the Middle East, with potential US casualties, to people at home? What happens next for Iran? In this special collaboration with Today in Focus, Annie Kelly speaks to the Guardian’s diplomatic editor, Patrick Wintour.