Question: Assess the main achievements of the first four caliphs (632 to 661 AD). How powerful and united was the Arab Empire at the death of Ali? {1996} Abu Bakr,, was the father-in-law of Mohammed and was the first converts to Islam. After the demise of Mohammed, Abu Bakar's main objective was to maintain the heritage of the prophet. However, distance tribes refused to recognize Abu Bakr's authority as their treaty relation was with the late Mohammed only. Thus after learning about the death of Mohammed, their nomadic instincts recoiled at the prospect of being subordinate to the men at Medina. These tribes refused alle