This book argues that the US Army has made four significant shifts in the content of its capstone operations doctrine along a spectrum of war since the end of WWII: 1) in 1954 it made a shift from a doctrine focused almost exclusively on mid-intensity conventional warfare to a doctrine that added significant emphasis to high-intensity nuclear warfare; 2) in 1962 it made an even greater shift in the opposite direction toward low-intensity unconventional warfare doctrine; 3) in 1976 it shifted back to an almost exclusive focus on mid-intensity conventional warfare content; 4) and this is where Army doctrine remained for 32 years until 2008, when it made a doctrinal shift back toward low-intensity unconventional warfare – five and seven years into the wars in Iraq and Afghanistan respectively. Closely tracking each of these shifts, the author zooms in on specific domestic, international and bureaucratic politics that had a direct impact on these shifts.