Early in 646 C.E. a large Byzantine force landed at Alexandria and occupied it. From the base at Alexandria, the Byzantines planned to reconquer the whole of Egypt. The Muslims of Egypt sent a delegation to Madina to prevail on Uthman to restore 'Amr b Al 'Aas and appealed to him to take over the command of Egypt. He stipulated some terms which were accepted by Uthman. 'Amr b Al 'Aas was made the Governor of United Egypt, and he was also to be the supreme commander of the military forces in Egypt. Abdullah b Sa'ad was to hold a subordinate position under 'Amr b Al 'Aas .
'Amr b A1 'Aas took over the command in Egypt and drove away the Byzantines from the soil of Egypt. After the reconquest of Egypt another crisis developed. As under Abdullah b Sa'ad the revenues of the province had risen considerably, Uthman made Abdullah b Sa'ad hold independent charge of the Revenue Department while 'Amr b Al 'Aas was to be the Governor and supreme commander of the military forces. 'Amr b A1 'Aas protested against this arrangement. He said that under such an arrangement he would be holding the cow by the horns while some one else would be milking it. Uthman desired that 'Amr b Al 'Aas should guarantee that the revenues would not fall below the stipulated level 'Amr b A1 'Aas was not prepared to give even such guarantee. The dispute could not be resolved and ultimately Uthman passed orders for the deposition of 'Amr b Al 'Aas .