Rosa Luxemburg holds an enduring fascination as a radical socialist committed to democratic values, and a woman whose charismatic personality and impassioned speeches inspired her followers without resort to bureaucratic organization. Her assistant and friend, Mathilde Jacob, was Luxemburg's mainstay during her years of imprisonment in World War I. Jacob provided material and emotional support, organized Rosa Luxemburg's clandestine communication with the outside world, and herself played a key role in the illegal work of the Spartacus group. When revolution broke out in Germany in 1918, she...