As more than a million protesters are said to have "flooded into central Cairo" this week, demanding an end to Hosni Mubarak's authoritarian rule, William Hartung, the director of the Arms and Security Initiative at the New America Foundation and author of Prophets of War: Lockheed Martin and the Making of the Military-Industrial Complex, explained a little understood fact about the "tens of billions of dollars" in US military aid used to prop up the authoritarian Mubarak regime.