The 3rd Rashidun Caliph, Uthman () continued the policy of military expansion carried out by his predecessors, Umar and Abu Bakr. During his reign, the caliphate stretched from Tripolitania, Egypt, and Anatolia to Greater Khorasan and Sindh and reached its greatest extent in 654 CE. However, these conquests were halted when a rebellion began in Egypt which led to his murder, and began the first Fitna.
Background Byzantine attempt to re-capture Egypt With the death of Umar and the disposal of 'Amr ibn al-'As from the governorship of Egypt, the Byzantines seized Alexandria, thinking it to be the right time to take action. Uthman again sent 'Amr ibn al-'As to defend Egypt and made him governor and commander-in-chief of Egypt. Amr defeated the Byzantine forces in the Battle of Nikiou, a few hundred miles from Fustat. After the defeat of the Byzantine army at Naqyus the Rashidun army laid siege to Alexandria, which fell when a Copt opened the gates of city one night, in return for amnesty.
After re-conquering Alexandria, 'Amr ibn al-'As ordered the demolition of the walls of the city to obstruct any future invasion by Byzantine forces. Amr was again dismissed from his post due to his loose financial administration
Campaigns Conquest of North Africa After the withdrawal of the Byzantines from Egypt, North Africa which was Byzantine Exarchate of Africa had declared its independence under its king, Gregory the Patrician. The dominions of Gregory extended from the borders of Egypt to Morocco. Abdullah ibn Saad would send raiding parties to the west and as a result of these raids the Muslims got considerable treasure. The success of these raids made Abdullah ibn Saad feel that a regular campaign should be undertaken for the conquest of North Africa.
Uthman gave him permission after considering it in Majlis al Shura and a force of 10,000 soldiers was sent as reinforcements. The army assembled at Barqah in Cyrenaica, and in 647 from there they marched west to capture Tripoli, after Tripoli they marched to Sbeitla, the capital of King Gregory. Gregory was defeated and killed in the battle due to the tactics used by Abd-Allah ibn al-Zubayr. After the battle of Sufetula the people of North Africa sued for peace and they agreed to pay an annual tribute. The Arabs had sacked Sufetula and raided across the Exarchate, while the Byzantines withdrew to their fortresses. Unable to storm the Byzantine fortifications, and satisfied with the huge amounts of plunder they had made, the Arabs agreed to depart in exchange for the payment of a heavy tribute in gold.Diehl (1896), pp. 559–560 Instead of annexing North Africa, the Muslims preferred to make it a vassal state and when the stipulated amount of the tribute was paid, the army withdrew to Barqah.
First Muslim invasion of Iberian Peninsula According to many books of Islamic history, the conquest of the Spanish section of the Iberian Peninsula is attributed to Tariq ibn-Ziyad and Musa bin Nusair in 711 – 712, in the time of the Umayyad Caliph, al-Walid I (Walid ibn Abd al-Malik). However, according to Muslim historian Muhammad ibn Jarir al-Tabari,See: History of the Prophets and Kings (Tarikh al-Tabari) Spain was first invaded some sixty years earlier during the caliphate of Uthman. Other prominent Muslim historians like, Ibn Kathir,See: Al-Bidayah wa al-Nihayah (Tarikh ibn Kathir) have also quoted the same narration.
According to the account of al-Tabari, when North Africa had been duly conquered by Abdullah ibn Saad, two of his generals, Abdullah ibn Nafi ibn Husain, and Abdullah ibn Nafi' ibn Abdul Qais, were commissioned to invade the coastal areas of Spain by sea. On this occasion Uthman is reported to have addressed a letter to the invading force. In the course of the letter, Uthman said:
No details of the campaigns in Spain during the caliphate of Uthman are given by Muhammad ibn Jarir al-Tabari or by any other historian. The account of al-Tabari is merely to the effect, that an Arab force aided by a Berber force landed in Spain, and succeeded in conquering the coastal areas of Al-Andalus. We do not know where the Muslim force landed, what resistance they met, and what parts of Spain they actually conquered. Anyhow, it is clear that the Muslims did conquer some parts of Spain during the caliphate of Uthman. Presumably the Muslims established some colonies on the coast of Spain. There are reasons to presume that these Muslims entered into trade relations with the rest of Spain and other parts of Europe. The areas were lost shortly after because of the general disorder in the empire.
Campaign against Nubia A failed campaign was undertaken against Nubia during the Caliphate of Umar in 642 at the first battle of Dongola. This was the Arabs' first real defeat on the battlefield despite outnumbering their opponents. The war ultimately ended in a baqt treaty, after the second battle of Dongola
Ten years later in 652, Uthman's governor of Egypt, Abdullah ibn Saad, sent another army to Nubia. This army penetrated deeper into Nubia and laid siege to the Nubian capital of Dongola. The Muslims demolished the cathedral in the center of the city. The Arabs retreated because of the Nubian archers who let loose a shower of arrows aimed at the eyes of the Muslim warriors. As the Muslims were not able to overpower the Nubians, they accepted the offer of peace from the Nubian king. According to the treaty that was signed, each side agreed not to make any aggressive moves against the other. Each side agreed to afford free passage to the other party through its territories. Nubia agreed to provide 360 slaves to Egypt every year.
Conquest of the islands of Mediterranean Sea During Umar's reign, the governor of Syria, Muawiyah I, sent a request to build a naval force to invade the islands in the Mediterranean Sea but Umar rejected the proposal because of risk of death of soldiers at sea. During his reign Uthman gave Muawiyah permission to build a navy after concerning the matter closely. The Muslim force landed on Cyprus in 649. There was only a small Byzantine garrison on the island, which was overpowered without any difficulty. The islanders submitted to the Muslims, and agreed to pay a tribute of 7,000 dinars per year. The conquest of Cyprus was the first naval conquest of the Muslims. After Cyprus, the Muslim naval fleet headed towards the island of Crete and then Rhodes and conquered them without much resistance. In 652–654, the Muslims launched a naval campaign against Sicily and they succeeded in capturing a large part of the island. Soon after this Uthman was murdered, no further expansion was made, and the Muslims accordingly retreated from Sicily. In 655 Byzantine emperor Constans II led a fleet in person to attack the Muslims at Phoiníkē (off Lycia) but it was defeated: 500 Byzantine ships were destroyed in the battle, and the emperor himself risked being killed.
Byzantine attempt to re-conquer Syria After the death of Umar, the Byzantine emperor, Constantine III, decided to re-capture the Levant, which had been lost to the Muslims during Umar's reign. A full-scale invasion was planned and a force of 80,000 soldiers was sent to re-conquer Syria. Muawiyah, the governor of Syria, called for reinforcements and Uthman ordered the governor of Kufa to send a contingent, which together with the Syrians defeated the Byzantine army.
Re-Conquest of Armenia and Georgia Armenia and Georgia were conquered during the reign of Umar. Initial raids took place under the command of Khalid ibn al-Walid and Ayadh bin Ghanim. Later Habib ibn Muslaimah was sent for a full-scale invasion up to the Black Sea. During Uthman’s reign, a revolt broke out, and Uthman commissioned Habib ibn Muslaimah to reassert their control over Armenia and Georgia. The whole of the region was re-conquered. There was not much fighting, and on the approach of the Muslim armies, the Armenians laid down arms, and accepted the usual terms of the payment of Jizya (tribute). Armenia, Georgia and Azerbaijan were made one province under the name Azerbaijan; Ashat ibn Qais was the last governor of this province during Uthman's reign.
Occupation of Anatolia The Byzantine forts in the region of Tarsus were conquered during Umar's reign, soon after the Conquest of Antioch, by Khalid ibn al-Walid and Abu Ubaidah ibn al-Jarrah. During Uthman's reign the region was recaptured by Byzantine forces and a series of campaigns were launched to regain control of the region. In 647 Muawiyah the governor of Syria sent an expedition against the Anatolia, they entered in Cappadocia, and sacked Caesarea Mazaca. In 648 the Rashidun army raided into Phrygia. A major offensive into Cilicia and Isauria in 650–651 forced the Byzantine emperor Constans II to enter into negotiations with Caliph Uthman's governor of Syria, Muawiyah. The truce that followed allowed a short respite, and made it possible for Constans II to hold on to the western portions of Armenia. In 654–655 on the orders of Caliph Uthman, an expedition was preparing to attack the Byzantine capital Constantinople but did not carry out the plan due to the civil war that broke out in 656. The Taurus Mountains in Turkey marked the westernmost frontiers of Rashidun Caliphate in Anatolia during Caliph Uthman's reign.
Re-conquest of Fars The province of Fars in Persia was conquered by the Muslims during the Caliphate of Umar. In Uthman's reign, like other provinces of Persia, Fars also broke into revolt. Uthman directed Abdullah ibn Aamir, the Governor of Basra, to take immediate steps to retrieve the situation. Accordingly, he marched with a large force to Persepolis; the city surrendered and agreed to pay tribute. From here the army marched to Al j bard, where, after a brief resistance, the Muslims captured the city, and the citizens agreed to pay tribute. Thereafter the Muslim force advanced to Jor. The Persians gave battle but they were defeated and the city was captured by the Muslims. Peace was made with the usual terms, the payment of Jizya. While the army was still in Jor, Persepolis again broke into revolt; Abdullah ibn Aamir then took his forces to Persepolis and laid siege to the city. After a violent battle the Muslims were able to regain control of the city once again. All of the leaders among the Persians who were involved in instigating the revolt were hunted down and executed. With the fall of Persepolis, other cities in Fars also submitted unconditionally. Thus the Muslims once again became the masters of Fars. Uthman's appointed governor of Fars, after analyzing the situation, sent Islamic missionaries to various cities of the region to convert the people to Islam to avert future revolts. A large number of people embraced Islam.
Re-conquest of Sistan In the 7th century, the Persian Empire's province of Sistan extended from the modern day Iranian province of Sistan to central Afghanistan and the Balochistan province of Pakistan.
Sistan was captured during the reign of Umar, and like other provinces of the Persian Empire, it also broke into revolt during Uthman's reign in 649. Uthman directed the governor of Bosra, Abdullah ibn Aamir to re-conquer the Persian province of Sistan. A column was sent to Sistan under the command of Rabiah ibn Ziyad. The first confrontation took place at Zaliq, a border town, during a Persian festival and with the Muslims victorious, the citizens asked for peace. It is said that the Muslim commander, Rabiah ibn Ziyad, stuck a pole in the ground and asked the Persians to pile gold and silver up to the top. Once it was done the Muslims left the citizens in peace.