I first met Andrew Marshall, the longtime director of the Pentagon’s Office of Net Assessment (ONA), in the mid-1990s. The occasion was one of the late Harvard professor Samuel P. Huntington’s “Strategy and National Security” conferences at the Wianno Club on Cape Cod. A number of Huntington’s students, including Eliot Cohen, Aaron Friedberg and my Olin Institute for Strategic Studies colleague Stephen Rosen, were also Marshall protégés—alumni of St. Andrew’s Prep, as they referred to themselves—having spent some of their careers under his tutelage in the ONA...