[Torie]

But if it was so good, why were not the newly installed Arabs send back to Mecca?

[AntiGuv]

*sigh*

[AntiGuv]

The thema system was not developed to its full glory until the reign of Constans II, by the 660s basically. By that time, the Empire had otherwise fallen into decline and would soon afterward also get wracked up for a century over the silliest of nonsensical religious conflicts (they were fighting over whether or not icons are idols). Egypt and Syria had been the wealthiest provinces of the Empire, along with Anatolia, and their loss was irreparable. In other words, by the time that the Byzantines were in shape again, they were robbed of the men and grain of Egypt & Syria which was now part of the Arab arsenal instead. Moreover, the Monophysites of those provinces were happier (at that time) under Muslim rule than they had been under Orthodox rule.