Map 3.1: The Byzantine and Bulgarian Empires, c.920
Another glance at the two maps reveals a second area of modest expansion, this
time on Byzantium’s eastern front. In the course of the ninth century the Byzantines
had worked out a strategy of skirmish warfare in Anatolia. When Muslim raiding
parties attacked, the strategoi evacuated the population, burned the crops, and, while
sending out a few troops to harass the invaders, largely waited out the raid within
their local fortifications. But by 860, the threat of invasion was largely over (though
the menace of Muslim navies—on Sicily and in southern Italy, for example—
remained very real). In 900, Emperor Leo VI (r.886–912) was confident enough to
go on the offensive, sending the tagmata in the direction of Tarsus. The raid was a
success, and in its wake at least one princely family in Armenia broke off its alliance
with the Arabs, entered imperial service, and ceded its principality to Byzantium.
Reorganized as the theme of Mesopotamia, it was the first of a series of new themes
that Leo created in an area that had been largely a no-man’s-land between the Islamic
and Byzantine worlds.
The rise of the tagmata eventually had the unanticipated consequence of
downgrading the themes. The soldiers of the themes got the “grunt work”—the
