A Sacred Oath: Memoirs of a Secretary of Defense During Extraordinary Times – An Instant New York Times Bestseller: A Pentagon Insider's Tumultuous Years Under President Trump

by Mark T. Esper

Fourth Estate—the collective name for DoD agencies and activities that are not part of the military branches, ranging from the OSD and the Joint Staff to the Defense Logistics Agency and Missile Defense Agency. There are more than two dozen of these organizations, and they include more than 380,000 people and spend more than $100 billion—nearly 15 percent of the entire DoD budget—annually.