who three years previously had overthrown Carausius
and proclaimed himself Augustus. In 297 Maximian was forced to appear in
person in Africa to suppress a revolt of the Quinquegentiani. Meanwhile,
Diocletian crushed a usurper named Achilles in Egypt and repulsed the
invading Blemyes. Galerius, under the orders of Diocletian, after
repelling attacks of the Iazyges (294 A. D.) and Carpi (296 A. D.), was
called upon to meet a Persian invasion of Armenia and Mesopotamia. He was
at first severely defeated, but, after being reinforced, won a decisive
victory over Narses, the Persian king, and recovered Armenia. Diocletian
himself won back Mesopotamia and the Persians were forced to acknowledge
the Roman suzerainty over Armenia, while the Roman frontier in Mesopotamia
was advanced to the upper Tigris. In all parts of the empire the border
defenses were repaired and strengthened.

*Army reforms; provincial organization.* The military reforms of
Diocletian aimed to correct the weakness revealed in the previous system
by the wars of the third century. He created a powerful mobile force--the
_comitatenses_; while organizing the permanent garrison along the frontier
in the form of a border militia--the _limitanei_. At the same time, the
military and civil authority in the provinces was sharply divided to
prevent a dangerous concentration of power in the hands of any one
official. And the same motive is to be traced in the subdivision of the
province, the number of which was raised to 101. These were grouped in
thirteen dioceses, administered by _vicarii_ (vicars), who were
subordinate to the praetorian prefects.

*The edict of prices, 301 A. D.* Diocletian also made a thorough revision
of the system of taxation, and tried, but without success, to establish a
satisfactory monetary standard. A more conspicuous failure, however, was
his attempt to stabilize economic conditions by government regulation. By
the Edict of Prices issued in 301, he fixed a uniform price for each
commodity and every form of labor or professional service throughout the
empire. The penalty of death was provided for all who demanded or offered
more than the legal price. The law proved impossible to enforce. It took
no account of the variations of supply and demand in the various parts of
the empire, of the difference between wholesale and retail trade, or in
the quality of articles of the same kind. In spite of the severe penalty
prescribed, the provisions of