Augustus
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I Think you need to read the history how these empires were destroyed
They fought each other too much leaving them weak and bankrupt, were affected badly by plague, many of their Arab tribe mercenaries went off to join the other tribes either because they weren't getting paid any more or there were richer pickings in raiding the Empires, etc.
Diverse groups of tribesman began raiding the Empires and over time they realised that there was little coming back at them which emboldened them to go further and further. Eventually there were sizable invasions rather than small raiding parties.
Being militarily weak, after losing a single major battle each, both of the 2 Empires were practically defenceless and easy to conquer.
The proto-Muslims were not the first group of tribesman to win battles against the major Empires, the only difference was that they were intent on conquering and occupation and settling whereas previous victors had mostly been content with looting and extracting large payments in tribute.
How do you see it happening?
But can you tell me why the Europeans colonized most of Africa and Asia
Same reason that the 'Arabs' colonised the ME and North Africa: ideology, money and power.
Islam means peace and totally against this horror
Do you believe that the expansion of the Rashidun Caliphate would be best characterised by the word 'peaceful'?
Why do you view it as being different from the Empire building of the Romans or the Persians, which was certainly far from peaceful.