In his surprisingly controversial 1976 book The Grand Strategy of the Roman Empire: from the First Century AD to the Third, military historian Edward Luttwak argued that the Empire had a conscious, evolving yet consistent strategy of "defense in depth," based on lines of frontier forts, backed by central mobile armies.

Now, in The Grand Strategy of the Byzantine Empire, Luttwak explains that after the collapse of the Western Empire in the 5^th Century AD, Eastern emperors no longer enjoyed this luxury. Faced by waves of nomadic horse archers from the steppes, plus Sassanid Persia, a traditional enemy to the East, the Empire could not afford to fight decisive battles or wars of attrition that would deplete the costly, carefully trained Imperial army.

The Empire evolved an "operational code" that combined diplomacy, intelligence, and well-placed bribery, as well as trade and cultural influence, with the application of military force by carefully organized and trained armies and navies as a last resort. If war was unavoidable, professionally trained Byzantine commanders used "relational maneuver" based on study of the strengths and weaknesses of each enemy, and strategic policy generally did not pursue the annihilation of the enemy, because it was often possible to bring a defeated foe into a future ally.

In the 7^th Century AD a new threat arose, Islam, with its aggressive religious ideology. appearing at a time of weakness due to the protracted Persian Wars (602-629). With disaffected religious minorities in Syria and North Africa provinces, the Empire was vulnerable and suffered grievously.  Yet it survived, and Luttwak demonstrates how a succession of warrior-emperors managed this threat for almost seven centuries.

The work examines the military organization and policy of the empire in great detail, and there is a valuable short, sharply argued chapter, "Leo VI and Naval Warfare" that reviews the limited surviving texts on Byzantine seapower, with an clear discussion of "Greek Fire," a very misunderstood "secret weapon."

The Grand Strategy of the Byzantine Empire is a work of solid scholarship, imagination and practical military analysis. It should be of more than antiquarian interest to those who believe that today's confrontation between Islam and the West is likely to be a multi-generational conflict.

The greatest shortcoming of the book is a crudely drawn, rather muddy set of maps. Readers will benefit from a good historical atlas such as The Penguin Atlas of Medieval History .