In 1986, Oxford University Press published The Uncensored War. An analysis by Daniel C. Hallin of media consumed in the United States during fighting in Vietnam, the monograph remains an important account of America’s first televised war. But a small diagram on page 117 would become the work’s greatest legacy: an illustration now referred to as “Hallin’s spheres.” To visualize the model, imagine a target made of two concentric circles, surrounded by a vast hinterland of empty space.