In your BoB podcast, you mentioned that the caliphate at the Second Arab Siege of Constantinople had 120,000 men ad at one point brought up reinforcements of ~750 ships. Are those numbers inflated? I’ll admit to not knowing much about medieval logistics, but fleets and armies that size seem to me to beyond their capacity.

Actually, I deliberately picked the low-end estimates. Some sources say that the Caliph’s armies were 200,000 strong, and his navies included some 5,000 ships. 

Keep in mind, we’re talking about the Umayyad Caliphate at the height of its powers, controlling an empire that includes this:

(“Umayyad750ADloc” by Gabagool – Own work. Licensed under CC BY 3.0 via Commons)

So the Umayyads are throwing everything that empire can muster at Constantinople.