The Eastern Romans were never very interested in expanding their borders; they were at a comfortable size at the time of Maurice or so in the East, and any more expansion would just have resulted in over-extension. Almost every time in the history of the Eastern Romans it was the Persians who started the hostilities. Now, I say EASTERN ROMANS, so don't say anything about Septimus or anything like that.
And a Turkish invasion would require massive coincidences coinciding together. A Turkish confederate breakup right at the same time as a Persian civil war with tribes near the border inclined to invade? Seems unlikely, especially considering these semi-independent border areas would never be involved with civil wars in the interior. There weren't that many, anyways; the Persians didn't really have a lot of infighting as succession was fairly flexible. When it did happen, it was catastrophic, but rare, so it would make it far more difficult for the Turks to invade.
And a Turkish invasion would require massive coincidences coinciding together. A Turkish confederate breakup right at the same time as a Persian civil war with tribes near the border inclined to invade? Seems unlikely, especially considering these semi-independent border areas would never be involved with civil wars in the interior. There weren't that many, anyways; the Persians didn't really have a lot of infighting as succession was fairly flexible. When it did happen, it was catastrophic, but rare, so it would make it far more difficult for the Turks to invade.