Kunitz then shifts his focus from exercise in times of leisure and abundance to warfare. He explains the key feature of the Roman army was group movement and cooperation. From running and swimming to archery and swordplay, soldiers trained to be well-rounded members of the team. Kunitz describes this as a period of skill development, when individuals exercised in order to meet a specific goal. This was true outside of the Roman Empire, as the martial arts were established in East Asia during this time as well. Similarly, in medieval Europe, knights mixed strength with skill through weighted sword training. This ethos extended beyond physical training and into the mind, too, through yoga, belief training, and visualization used by soldiers preparing for battle and religious practitioners alike.