Muawiyah I's family, including his progenitors, Abu Sufyan ibn Harb and his wife Hind bint Utbah, were originally opponents of Islam and particularly of Muhammad until the Conquest of Mecca, but they converted to the religion in 630.
However, many early history books, e.g., The Islamic Conquest of Syria Fatuhusham, by al-Imam al-Waqidi, state that, after their conversion to Islam, Muhammad appointed Muawiyah I's father Abu Sufyan ibn Harb and his brother Yazid ibn Abi Sufyan as army commanders.
Muawiyah I, Abu Sufyan ibn Harb, Yazid ibn Abi Sufyan and Hind bint Utbah fought in the Battle of Yarmouk.
The defeat of the Byzantine Emperor Heraclius at the Battle of Yarmouk opened the way for Muslim expansion into Jerusalem and Syria.

In 639, Muawiyah was appointed as the governor of Syria by the second caliph, Umar, after the two previous governors—his brother Yazid ibn Abi Sufyan and, before him, Abu Ubaidah ibn al-Jarrah—died in a plague along with 25,000 other people. '
Amr ibn al-'As was sent to take on the Roman Army in Egypt.
Umar asked Muawiyah to defend against an anticipated Roman attack.
Muawiyah next set about creating allies.
Muawiyah married Maysum, the daughter of the chief of the Kalb tribe, a large Jacobite Christian Arab tribe in Syria.
His marriage to Maysum was politically motivated.
The Kalb tribe had remained largely neutral when the Muslims first went into Syria.
Muawiyah now could use the Jacobite Christians to restore the ranks of the plague-depleted army against the Romans.
Muawiya's wife Maysum (Yazid's mother) was also a Jacobite Christian.
With limited resources and the Byzantines just over the border, Muawiyah worked in cooperation with the local Christian population.
To stop Byzantine harassment from the sea during the Arab-Byzantine Wars, in 649 Muawiyah set up a navy, which was manned by Monophysite Christians, Copts, and Jacobite Syrian Christian sailors and Muslim troops.

Muawiya was one of the first to realize the full importance of having a navy; as long as the Byzantine fleet could sail the Mediterranean unopposed, the coastlines of Syria, Palestine and Egypt would never be safe.
Muawiyah, along with Adbullah ibn Sa'd, the new governor of Egypt, successfully persuaded Uthman to give them permission to construct a large fleet in the dockyards of Egypt and Syria.
The first real naval engagement between the Muslim and the Byzantine navy was the so-called Battle of the Masts (Dhat al-sawari), or Battle of Phoenix, off the Lycian coast in 655, where the resulting Muslim victory opened up the Mediterranean.
Muawiyah I came to power after the death of Ali and established a dynasty.
Muawiyah I's family, including his progenitors, Abu Sufyan ibn Harb and his wife Hind bint Utbah, were originally opponents of Islam and particularly of Muhammad until the Conquest of Mecca, but they converted to the religion in 630. However, many early history books, e.g., The Islamic Conquest of Syria Fatuhusham, by al-Imam al-Waqidi, state that, after their conversion to Islam, Muhammad appointed Muawiyah I's father Abu Sufyan ibn Harb and his brother Yazid ibn Abi Sufyan as army commanders. Muawiyah I, Abu Sufyan ibn Harb, Yazid ibn Abi Sufyan and Hind bint Utbah fought in the Battle of Yarmouk. The defeat of the Byzantine Emperor Heraclius at the Battle of Yarmouk opened the way for Muslim expansion into Jerusalem and Syria.
In 639, Muawiyah was appointed as the governor of Syria by the second caliph, Umar, after the two previous governors—his brother Yazid ibn Abi Sufyan and, before him, Abu Ubaidah ibn al-Jarrah—died in a plague along with 25,000 other people. 'Amr ibn al-'As was sent to take on the Roman Army in Egypt. Umar asked Muawiyah to defend against an anticipated Roman attack. Muawiyah next set about creating allies. Muawiyah married Maysum, the daughter of the chief of the Kalb tribe, a large Jacobite Christian Arab tribe in Syria. His marriage to Maysum was politically motivated. The Kalb tribe had remained largely neutral when the Muslims first went into Syria. Muawiyah now could use the Jacobite Christians to restore the ranks of the plague-depleted army against the Romans. Muawiya's wife Maysum (Yazid's mother) was also a Jacobite Christian. With limited resources and the Byzantines just over the border, Muawiyah worked in cooperation with the local Christian population. To stop Byzantine harassment from the sea during the Arab-Byzantine Wars, in 649 Muawiyah set up a navy, which was manned by Monophysite Christians, Copts, and Jacobite Syrian Christian sailors and Muslim troops.
Muawiya was one of the first to realize the full importance of having a navy; as long as the Byzantine fleet could sail the Mediterranean unopposed, the coastlines of Syria, Palestine and Egypt would never be safe. Muawiyah, along with Adbullah ibn Sa'd, the new governor of Egypt, successfully persuaded Uthman to give them permission to construct a large fleet in the dockyards of Egypt and Syria. The first real naval engagement between the Muslim and the Byzantine navy was the so-called Battle of the Masts (Dhat al-sawari), or Battle of Phoenix, off the Lycian coast in 655, where the resulting Muslim victory opened up the Mediterranean. Muawiyah I came to power after the death of Ali and established a dynasty.
Umayyad Caliphate