The influential American strategist Andrew Marshall—affectionately known as Yoda within the U.S. national security establishment—joined the newly formed RAND Corporation in 1949 and later set up the Pentagon’s Office of Net Assessment, which he headed for more than four decades before retiring earlier this year at the age of 93. Krepinevich and Watts, two of Marshall’s close associates, have written an interesting examination of Marshall’s role in shaping American thinking on key defense issues: the potential vulnerability of U.S. strategic bases to a surprise Soviet nuclear attack, the burden of the defense sector on the Soviet economy, the so-called revolution in military affairs that might (or might not) have taken place during the 1990s, and the rise of China. But the authors shed little light on the meaning and methodology of “net assessment”; readers might conclude that it simply means that Marshall spent a lot of time worrying about threats. Marshall was unquestionably a giant in the field, and yet somehow he appears to have said very little and left few traces of his contributions. This helps explain his professional durability, but it also makes him a frustrating subject for an intellectual biography.