In 1976, military analyst Edward Luttwak published The Grand Strategy of the Roman Empire: from the First Century AD to the Third. He argued that the Empire practiced a conscious strategy of “defense in depth,” based on frontier fortifications, backed by central mobile armies to intercept barbarian incursions that penetrated the border zone.

In his new book, The Grand Strategy of the Byzantine Empire, Luttwak explains how, after the collapse of the Western Empire in the 5^th century AD, Eastern emperors could no longer afford the luxury of such defense in depth. Facing waves of fast-moving horse archers from the steppes (plus continuing threats from Persia, the traditional enemy,) the Empire had to avoid wars of attrition that would deplete its expensive, carefully trained professional army. With a far more limited population and tax base than earlier centuries offered, the later Empire urgently needed a new strategy for survival.

In the 7^th century AD a new threat with an aggressive faith emerged: Islam. With its own disgruntled religious minorities in Syria and North Africa, the Empire faced disintegration. Arab armies of conquest were greeted as liberators because they offered indigenous populations lower tax rates, and greater religious toleration. Luttwak explains how Byzantine rulers successfully managed this threat for seven long and sometimes bitter centuries.

The Empire evolved an “operational code” that did not depend on the low probability of getting a military genius as Emperor. Of 72 men (plus four women) who sat on the throne of Constantinople between 491 and 1453 AD, perhaps eight could be rated as warrior-emperors or “great Captains:” Maurice, Herakleios, Leo III, Nikeforos Phokas, John Tzimiskes, Basil II, Michael VIII and the tragic Constantine XI, who fell in action during the final Turkish assault on the walls of the city.

Luttwak distills seven fundamental principles from his keen analysis of the surviving Byzantine military manuscripts:

1. Avoid war by all possible means, but always be ready for it.
2. Gather intelligence to understand your enemy’s culture and mind-set.
3. Attack with small units; emphasize patrolling, raiding and skirmishing.
4. Wear out your enemy with protracted campaigns, not great battles.
5. Actively recruit allies to shift the balance of power.
6. Subversion is cheaper than combat; don’t send troops if a few sacks of gold will do the job.
7. Practice “relational maneuver” that avoids your enemy’s strengths and exploits his weaknesses.

The only real defect of the book is a set of poorly drawn, muddy-looking maps. Readers will therefore benefit from keeping a good historical atlas at hand (for example the Penguin Atlas of Medieval History).

The Grand Strategy of the Byzantine Empire is a worthwhile investment of reading time for planners and warfighters facing the prospect of multi-generational conflict in the same region, against some of the very same peoples that the Byzantines fought. Tactics and technologies may change as centuries pass, but the core principles of grand strategy endure.