Complex sentence: In the time of the British Mandate of Palestine the citadel in the old city of Acre was used as a prison, In which many Arabs were imprisoned as criminals or for participating in the Arab revolt.
Split into simpler sentences: In the time of the British Mandate of Palestine the fortress in the old city in Acre used as a prison. In this prison many Arabs were imprisoned as criminals and other Arabs were imprisoned as a result of their participation at the Arab revolt.