How political and military conflict cause famine

South Sudan and Yemen are at the brink of a severe food crisis, with over 400,000 malnourished children in Yemen, the United Nations estimates. Alex De Waal, a Tufts professor who spent years in the Horn of Africa, talks to Megan Thompson about his new book, “Mass Starvation: The History and Future of Famine” and how military conflict causes famine.