ADMINISTRATIONopment were greatest at the lowest level of the hierarchy, where a
subdistrict often consisted of the territory along a canal, and in the
region along the lower courses of the Tigris and Euphrates rivers,
where such changes were the greatest in this period.
The greatest degree of continuity appears to have been at the in-
termediate level of the district (kura), where the Sasanian names sur-
vived. However, the appearance of continuity at the district level is
somewhat illusory because of changes in the larger units to which they
belonged and in the smaller units which composed them. Some districts
do not appear to have functioned immediately after the conquest, such
as those in Ard Jukha or the district of Behrasir. Better evidence exists
in this part of Iraq for the survival of sub districts and their local
officials. Such districts appear to have been revived or reconstituted
in the early Islamic period-Behrasir by the time of 'An, and Shadh
Qubadh/Jalula by the late seventh century.
Continuity might also be measured in the degree to which early
Islamic administration in Iraq was hierarchic. It appears, in fact, to
have been highly hierarchic, especially in Ard Kufa, with many of the
subordinate units inherited from the Sasanians. But the shape of this
hierarchy was different, it was organized in a different way, and its
subordination to Kufa instead of to Mada'in reversed the Sasanian
organization.
There was also continuity in the preservation of the military nature
of certain frontier districts such as Anbar and 'Ayn Tamr under the
Muslims. But the emergence of Hulwan as a military center appears
to be new in the Islamic period, resulting from the way the conquest
shifted the important defensive frontier from southwestern Iraq against
the Arabs to the northeast against the Iranian plateau. Sasanian admin-
istration appears to have been military in Maysan and Dast-i Maysan
at the time of the conquest, but it was more fiscal under the Muslims.
However, the administration of districts such as Kaskar seems to have
been mainly fiscal under both regimes.
Administrative procedures and the geographical structure through
which they operated depended largely on the people who were involved
and affected by them. The counterpart to administrative geography is
human geography. In order to understand the process of continuity
and change more fully it is necessary to consider the geographical and
social distribution of the people of Iraq.