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How did Justinian I use forts, treaties, and subsidies to defend the Balkan frontier?
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Justinian I
Justinian I, detail of a mosaic in the Church of San Vitale, Ravenna, Italy.
To defend the Balkan frontier against continual incursions by Bulgars, Slavs, and other groups, Justinian I employed a multifaceted strategy of fortification and diplomacy.12
- Fortifications: Justinian expanded and strengthened a defensive system consisting of fortresses, strongholds, and watchtowers. This network ran in three zones across the Balkans, extending as far south as the Pass of Thermopylae, to protect the provinces of Thrace, Dacia, and Dalmatia.12
- Diplomacy and Subsidies: Recognizing that military manpower was scarce, Justinian’s administration relied heavily on diplomacy to manage the diverse groups pressing against the frontier. This included using bribes and subsidies to "buy off" invaders, such as the Avars in 561.12
- Strategic Alliances: Byzantine agents frequently used "defensive imperialism," employing bribery and treaties to pit one barbarian group against another. For example, the empire successfully bribed the Utigurs to attack the Kutrigur Bulgars, weakening both groups and preventing further incursions.2
Despite these efforts, the frontier remained vulnerable, and the empire struggled to effectively repel or assimilate the newcomers, who eventually succeeded in settling within the Roman provinces.12