“One of my favorite ideas is, never to keep an unnecessary soldier,” Thomas Jefferson wrote in 1792. Neither Jefferson nor the other Founders could ever have envisioned the modern national security state, with its tens of thousands of “privateers”; its bloated Department of Homeland Security; its rusting nuclear weapons, ill-maintained and difficult to dismantle; and its strange fascination with an unproven counterinsurgency doctrine. Written with bracing wit and intelligence, Rachel Maddow’s Drift argues that we’ve drifted away from America’s original ideals and become a nation weirdly at peace with perpetual war, with all the financial and human costs that entails. To understand how we’ve arrived at such a dangerous place, Maddow takes us from the Vietnam War to...