In a treaty signed with the Byzantine governor Cyrus, Amr guaranteed the security of Egypt's population and imposed a poll tax on non-Muslim adult males.

After gradually diluting Amr's authority, Caliph Uthman (r. 644–656) dismissed him in 646 after accusations of incompetency from his successor Abd Allah ibn Sa'd.

In the ensuing First Fitna, Amr joined Mu'awiya ibn Abi Sufyan against Caliph Ali (r. 656–661) due to promises of the governorship of Egypt and its tax revenues.

Afterward, he wrested control of Egypt from Ali's loyalists, killing its governor Muhammad ibn Abi Bakr, and assumed the governorship instead.

[11] Amr conditioned his conversion on the forgiveness of his past sins and an "active part in affairs", according to a report cited by the historian Ibn Asakir (d.

[13] The purpose of the raid is unclear, though the modern historian Fred Donner speculates that it was to "break up a gathering of hostile tribal groups" possibly backed by the Byzantine Empire.

Amr was personally chosen by Muhammad to deliver a letter calling the kings of Oman, the Julanda brothers Abd and Jayfa, to convert to Islam while being accompanied by Sa'id ibn Aws al-Ansari.

Historian Al-Baladhuri reports that on their departure to Sohar, Muhammad said to them: "If these people (of Oman) accept the witness of truth and pledge obedience to Allah and his Prophet, Amr will be the commander, and Abu Zayd will officiate in prayer.

Muhammad's successor Caliph Abu Bakr (r. 632–634) appointed Amr to rein in the apostate Quda'a tribes, and among those targeted were the Hejazi branches of the Bali.

[20] Amr's campaigns, which were supported by the commander Shurahbil ibn Hasana, succeeded in restoring Medina's authority as far as the northern frontier with Syria.

[24] After the negotiations broke down, Amr's men bested the Byzantines at the Battle of Dathin on 4 February 634 and set up headquarters at Ghamr al-Arabat in the middle of the Wadi Araba.

[24][26] Most accounts hold that Amr's army was 3,000-strong; the Muhajirun (emigrants from Mecca to Medina) and the Ansar (natives of Medina), who together formed the core of the earliest Muslim converts, dominated his forces according to al-Waqidi (d. 823), while the 9th-century historian Ibn A'tham holds that Amr's army consisted of 3,300 Qurayshite and allied horsemen, 1,700 horsemen from the Banu Sulaym and 200 from the Yemenite tribe of Madh'hij.

[27] The historian Philip Mayerson considers the troop figures to be "unquestionably exaggerated" but still representing the largest Arab fighting force to have ever been assembled in southern Palestine and the Sinai until then.

[40][41] Abu Ubayda led the siege of Jerusalem, in which Amr participated, but the city only surrendered after Caliph Umar arrived in person to conclude a treaty with its defenders.

It fell virtually without resistance after Cyrus, who had since been restored to office, and Amr finalized a treaty in Babylon guaranteeing the security of Egypt's inhabitants and imposing a poll tax on adult males.

He besieged and captured Alexandria in the summer of 646; most of the Byzantines, including Manuel, were slain, many of its inhabitants were killed and the city was burned until Amr ordered an end to the onslaught.

[61] He originally intended for Alexandria to serve as the Arabs' capital in Egypt, but Umar rejected this on the basis that no body of water, i.e. the Nile, should separate the caliph from his army.

[77] Accounts vary as to the number of troops Amr garrisoned in the city, ranging from 1,000 soldiers from the Azd and Banu Fahm tribes to a quarter of the army which was replaced on a rotational basis every six months.

[79] He imposed other measures, sanctioned by Umar, that entailed the inhabitants' regular provision of wheat, honey, oil and vinegar as a subsistence allowance for the Arab troops.

[84] Amr acted relatively independent as governor and retained much of the surplus tax revenue of the province for the benefit of its troops despite pressure from Umar to forward proceeds to Medina.

[82] Umar's successor Caliph Uthman (r. 644–656) initially kept Amr in his governorship and forged marital links with him by wedding to him his maternal half-sister Umm Kulthum bint Uqba ibn Abi Mu'ayt.

[82] Ibn Sa'd reduced the fiscal privileges of Egypt's original Arab military settlers, who had been shown favor by Amr, and secured the remittance of the surplus to Medina.

In a sermon at the mosque in Medina in June 656 and a letter penned to the Muslim leaders in Syria, Uthman mentioned that he had intended to reappoint Amr but did not follow through as a result of the latter's excessive insult.

[106][107] The roughly 400–600 Egyptian mutineers had protested Uthman's fiscal centralization policies in Medina and accused him of favoring his relatives over the early Muslim converts.

[89] The Caliph persuaded them to withdraw, but after they intercepted a letter on their departure ordering Ibn Abi Sarh to punish them, they turned back and assaulted Uthman in his home.

[115] When Ali's army set up camp around Siffin, south of the Euphrates town of Raqqa, in early June, Mu'awiya's advance guard led by Abu al-A'war refused them access to the watering places under their control.

[116] After Ali protested, Amr advised Mu'awiya to accept their request as preventing access to water might rally the hitherto demotivated Iraqis to a determined fight against the Syrians.

[118] As head of the Syrian cavalry,[4] Amr held the overall field command for Mu'awiya's forces in the ensuing weeks-long Battle of Siffin and on occasion personally participated in direct combat, though without particular distinction.

[127] As early as 656/57, Amr and Mu'awiya persuaded Ibn Abi Hudhayfa, who had seized control of Egypt after Uthman's assassination, to meet them in al-Arish, where they took him captive in a ruse.

680–690), who was generally critical of Arab rule, said of Amr that he "had no mercy on the Egyptians, and did not observe the covenant they had made with him",[139] but also says of him that: "He exacted the taxes which had been determined upon but he took none of the property of the churches, and he committed no act of spoliation or plunder, and he preserved them throughout all his days.