the 1040s when their raiding bands began to lay waste the easternmost themes of the empire and the nomadic tribes who followed in their wake began to encroach upon the pasture lands of the Anatolian plateau. The Armenian and Georgian client princes of the empire held them back as long as they could, but were forced to flee into the Caucasus or southwards towards Cilicia. The armed forces, so successful in the previous century, were now involved in the power politics of Constantinople or in attempting to stem attacks on the western lands of the empire. It is of some significance that the Byzantine defeat at Mantzikert ( 1071) at which the Emperor Romanus IV Diogenes fell into the hands of the Turks took place in the same year that Norman forces captured Bari, the capital of Byzantine Italy. Not for the first time in imperial history, the challenge of maintaining the defence of long frontiers from a distant capital was to prove almost too great. By the time the forces of the First Crusade arrived in Constantinople in 1097, the Byzantines had issued a series of appeals to the west for help against the infidel and many 'Franks' had responded by joining the increasingly polyglot mercenary forces of the emperor: Germans, Varangians (Scandinavians), Russians, and even English amongst them.
The costs of the warfare of the later eleventh century took their toll of the imperial revenues. Whilst the debasements of the coinage which took place in the first half of the century can now be seen as attempts to increase the amount of coin in circulation to take account of buoyant production of both agrarian and manufactured goods, by the reign of Alexius Comnenus the most serious drain on imperial resources was the payment and equipping of the troops levied to fight the Turks in the east, the nomadic incursions across the Danube, and Norman intervention in Italy and the Balkans. It is no wonder that Theophylact, archbishop of Ohrid at the turn of the eleventh and twelfth centuries, could complain of the 'locust-like' presence of the imperial armies and tax-collectors in the Balkans and the apparent lack of concern in Constantinople for the plight of the provinces. Alexius Comnenus' reform of the currency and the system of gathering taxes went
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