Final answer:
Diocletian reorganized the Roman Empire by introducing the Tetrarchy, splitting the governance between four rulers and subdividing the Empire into more manageable provinces, in part to enhance military efficiency and control.
Step-by-step explanation:
The Roman Emperor Diocletian implemented significant reforms to stabilize and manage the Roman Empire. Recognizing the challenges posed by administering the vast empire, Diocletian reorganized political governance by introducing the Tetrarchy, a system of co-rulers. This division of the empire into two parts allowed for more efficient management, with Diocletian ruling the eastern half and his co-emperor Maximian ruling the west. Further restructuring occurred with two junior emperors, or Caesars, joining the governance scheme. Moreover, Diocletian subdivided the Empire into smaller provinces and established the positions of vicars to oversee these areas. These reforms created a more manageable governmental structure that endured beyond his reign.
Aside from the Tetrarchy, Diocletian reformed the Roman military, recruiting more soldiers, emphasizing heavy cavalry, creating new roads for military use, and making legions smaller to prevent any single commander from usurping power. His reforms laid the groundwork for the Empire's eventual eastward shift, effectuating long-lasting impacts on the political and military architecture of ancient Rome.
Different from the student's options, the correct answer is that Diocletian divided the empire into two parts for easier management, corresponding to choice (c) in the multiple-choice question.