Let us suppose both that Justinian's reconquests go better and are retained longer (so they hold onto all of Italy and a good chunk of Hispania), and that Islam bursts onto the scene around the same time. We shall also assume a comparably futile and damaging war with Persia as historically happened. Yes, these are very narrow constrictions.
How might the ensuing wars play out? On the one hand, the Empire has more resources. On the other, they have more to defend. The Arabs would not be the only threat, after all. The Visigoths might likely be holding a grudge, for example.
How might the ensuing wars play out? On the one hand, the Empire has more resources. On the other, they have more to defend. The Arabs would not be the only threat, after all. The Visigoths might likely be holding a grudge, for example.