While the armies of the Roman Empire, including its late 'Byzantine' phase, have been copiously studied, naval warfare of the period has been neglected. In part this is due to relative paucity of the available sources but Augustine H Kobayashi demonstrates that this does not imply a lack of maritime activity in this period; in fact quite the opposite is true. This compelling book delves into the profound significance of naval and maritime power in shaping the destinies of ancient empires, with a particular focus on the Empire of the Romans in the East. This 'Byzantine Empire', thrived remarkably for centuries—its longevity attributed to its formidable sea power. The imperial fleet played crucial roles in the Empire’s reconquest of the West by Justinian I, its struggles against the Muslim Arabs, (which turned the Mediterranean into a naval war zone,) as well as its resurgence in the tenth and eleventh centuries. The Age of Crusade was also about the changing balance of power at sea at the expense of the Byzantine Empire, which signalled the rise of the Latin West. The main narrative vividly explores the empire’s pivotal history from its zenith in the sixth century, a time when the remnants of the Roman Empire aspired to restore its former glory, to its demise at the hands of the Westerners in the early thirteenth century. The Byzantine navy not only provided critical logistical support to its armies but also facilitated the reclamation of lost territories and the triumph over formidable adversaries.