SPINE BIOMECHANICS PROVIDE the foundation for the disciplines of spine medicine and spine surgery. Although modern spine biomechanics emerged during the second half of the last century, it has many ancient, medieval, and post-Renaissance roots. In Part I of this series, the ancient and medieval roots of spine biomechanics were reviewed. In Part II, the effects of post-Renaissance scientists on the development of modern spine biomechanics, as well as the studies on gait, bone, and muscles performed before the 20th century, are reviewed. Subsequently, war-related studies performed in the 20th century contributed to the formation of modern biomechanics. The first biomechanics-related organizations and scientific publications did not emerge until the second half of the 20th century. These events provided the final bricks in the foundation that facilitated the emergence of modern spine biomechanics research.