Military expansion. The Rashidun Caliphate expanded gradually; within the span of 24 years of conquest, a vast territory was conquered comprising Mesopotamia, the Levant, parts of Anatolia, and most of the Sasanian Empire. Unlike the Sasanian Persians, the Byzantines, after losing Syria, retreated back to Anatolia.
1 And the nature of this reality again can neither be consistently represented as a fixed and hard substance nor as an unalterable something, but only as a fixed order of recurrence of continually changing events or impressions.
adjective. 1  Refusing to give up or let go; persevering obstinately. 2  Insistently repetitive or continuous: a persistent honking of car horns. 3  Existing or remaining in the same state for an indefinitely long time; enduring: persistent rumors; a persistent infection. Botany Lasting past maturity without falling off, as the calyx on an eggplant or the scales of a pine cone. Zoology Retained permanently, rather than disappearing in an early stage of development: the persistent gills of fishes.