THE CHRISTIAN REALMS 231were reoccupied. At the same time a gradual eastward expansion of
the realm into Alava in the upper Ebro valley brought it into conflict
with the neighbouring kingdom of Pamplona and the power of
the Banu Qasi, who from their strongholds in Tudela, Huesca and
Zaragoza' were seeking to dominate the region. However, the defeat
of their leader Musa and his son-in-law King Garcia of Pam pIon a by
Ordono I at Albelda in 859 established Asturian hegemony in Alava
for the next half century.
During the middle of the ninth century the region of Castille,
between the Asturian kingdom and the towns of the north-western
Meseta on the one hand and the upper Ebro valley on the other,
began to be developed. It was an area lacking in m3Jor urban settle-
ments, and its principal town of Burgos was not founded until 884,
but, as its name implies, it was a region of castles, small fortresses and
strongholds. Its early history is obscure despite its subsequent promi-
nence as the greatest Christian Spanish kingdom of the later Middle
Ages. In the ninth and tenth centuries it was just a vulnerable frontier
zone of the Asturian kingdom, but one whose nobility and their fol-
lowers enjoyed greater privileges and freedom from royal control
than other parts of the state in the interests of promoting settlement
and the resources for self-defence. Authority in Castille was exercised
by a count appointed by the king but enjoying a large measure of
practical independence. Even some of the earliest charters from the
region juxtapose the names of the king 'ruling in Oviedo' and the
count 'ruling in Castille'. In the time of Ordono I this was a Count
Didacus (Diego).14
It was in Castille that the new king Alfonso III 'the Great' (866-
910) had to take refuge soon after succeeding his father, expelled
from his throne by Froila, Count of Galicia, possibly a rival member
of the dynasty. However, the usurper was promptly murdered by some
of Alfonso's supporters and a remarkable reign was begun. The princi-
pal success of Alfonso's rule lay in the carrying to completion of the
occupation and extensive repopulation of the Duero valley and Castille
commenced by his father, aided by the political disintegration of the
Umayyad frontier marches, which now made possible a southward
extension of the Asturian kingdom. Settlements were either founded
or restored in such naturally defensible sites as Zamora and Toro,
which together with Leon became the centres of the colonisation of
the north-western Meseta. These strongholds became the targets for
attack by expeditions from the south, which continued sporadically