@Basileus Giorgios You said that the Byzantine Empire was substantially more powerful than the Arab Caliphate. I assumed you referred to the entirety of the Abbasid period, not just to the 900s. I also highly disagree, the Abbasids in the 870s, while in big trouble, could still recover. Al-Muhtadi's defeat of Ya'qub al-Saffarid and the continued Abbasid containment of various enemies. The wars and issues the Abbasid faced was simply too much, to retake the lands from the loss at Poson.
I knew Amorium recovered to existing, but certainly not to its previous situation of being the largest city in Anatolia.