The US Marine Corps has traditionally been one of the most innovative branches of the US military, but even it has struggled to learn and retain lessons from past counterinsurgency wars. Jeannie L. Johnson looks at the clash between strategic culture and organizational learning through the US Marine Corps's long experience with counterinsurgency. She first undertakes a fascinating examination of what makes the Marines distinct: their identity, norms, values, and perceptual lens. To do this, Johnson uses an innovative framework for analyzing strategic culture. Next, she traces the history of the Marines' counterinsurgency experience from the expeditionary missions of the early twentieth century, through the Vietnam War, and finally to the Iraq War. She shows that even a service as self-aware and dedicated to innovation as the US Marine Corps is significantly constrained in the lessons-learned process by its own internal predispositions. Even when internal preferences can be changed, ingrained biases endemic to the broader US military culture and American public culture create barriers to learning.