[cross-posted at Austro-Athenian Empire]
Writing of the defeat of the Byzantine forces at Brindisi in 1156, John Julius Norwich observes:
It was the same old lesson a lesson that should by now have been self-evident, but one that the princes of medieval Europe seemed to find almost impossible to learn: that in distant lands, wherever there existed an organized native opposition, a temporary occupying force could never achieve permanent conquest. Whirlwind campaigns were easy, especially when backed by bribes and generous subsidies to the local malcontents; when, however, it became necessary to consolidate and maintain the advantage gained, no amount of gold was of any avail. ... The outcome of the recent campaign however promisingly it had begun had not been unlucky. It had been inevitable.
(Byzantium: The Decline and Fall (NY: Knopf, 1995), pp. 115-116.)