Final answer:
The success of the Arab-Islamic conquests was due to effective military tactics, religious zeal among united tribes, and exploiting political instability in neighboring empires.
Step-by-step explanation:
The factors that led to the success of the Arab-Islamic conquests of the seventh and eighth centuries can be attributed to military tactics and superior weaponry, religious zeal and unity among the Arab tribes, and the political instability of neighboring empires. The Arab armies were highly mobile due to their use of horses and camels, which allowed for swift attacks and facilitated transportation of supplies. Coupled with their adeptness at siege warfare and intelligence-gathering, they could efficiently conquer lands. Additionally, the Persians and Byzantines had been weakened by incessant wars against each other, creating a ripe opportunity for the Arabs. Finally, the unity among the Arab tribes, propelled by a religious mission to spread Islam, created a strong and motivated fighting force.