Muawiyah had sent an army under his son Yazid against the Roman Empire as early as 668.

Yazid, reachingas far as Chalcedon, hasd taken the important imperial center Amorion.

Although the city had been quickly recovered, the Arabs had next attacked Carthage and Sicily in 669.

In 670, the Arabs had captured Cyzicus and established a base from which to launch further attacks into the heart of the Empire.

Their fleet captured Smyrna and other coastal cities in 672.

Finally, in 672, the Arabs sent a large fleet to attack Constantinople by sea.

While the emperor, Constantine IV, was diverted by this action, the Slavs had unsuccessfully attacked Thessalonika.

The victories had ended in 674, however, when the first naval siege of Constantinople itself proved to be a catastrophe due to the defender’s effective use of Greek fire, invented around 670 in Constantinople by Kallinikos (Callinicus), an architect from Heliopolis in the Roman Iudaea Province.

Twentieth-century British chemist and historian James Partington will posit that "Greek fire was really invented by the chemists in Constantinople who had inherited the discoveries of the Alexandrian chemical school".

Many accounts note that the fires it caused could not be put out by pouring water on the flames—on the contrary, the water served to intensify or spread them, suggesting that 'Greek fire' may have been a 'thermite-like' reaction, possibly involving a quicklime or similar compound.

Others have posited a flammable liquid that floated on water, possibly a form of naphtha or another low-density liquid hydrocarbon, as petroleum was known to Eastern chemists long before its use became widespread in the 1800s.

The Middle East: 676–819 CE

Islamic Expansion, Cultural Integration, and Dynastic Transformations

Consolidation and Revolts under the Umayyads

Following the establishment of the Umayyad Caliphate (661–750) with its capital in Damascus, the region undergoes significant political and cultural transformations. Muawiyah, founder of the dynasty, cements Umayyad control through administrative reforms, military strength, and religious tolerance, particularly toward Christians. Damascus flourishes, becoming one of the great cities of the eighth century, a hub of Islamic governance, culture, and economic prosperity.

However, succession issues plague the Umayyad dynasty. The violent death of Husayn ibn Ali at the Battle of Karbala (680) creates a profound schism between Sunni and Shia Muslims, deeply influencing Islamic history. The martyrdom of Husayn solidifies Shia identity, with Karbala and the tomb of his father Ali at Najaf becoming central pilgrimage sites.

Sectarian Divisions and Ideological Movements

This era sees the rise of multiple Islamic sects, each interpreting leadership and theology distinctively. The Kharijites, initially rebels from Ali's army, promote strict doctrinal adherence and lead rebellions in Iraq and beyond, notably influencing movements such as the Azraqi Kharijites who rebel in 685. Meanwhile, the rise of the Paulicians in Armenia around 664 introduces a dualistic Christian sect influenced by Gnostic beliefs, opposing the established church and empire.

Abbasid Revolution and Cultural Renaissance

The growing dissatisfaction with Umayyad rule culminates in the Abbasid Revolution led by Abu Muslim, who captures Iraq in 747 and establishes the Abbasid Caliphate in 750 with its capital in Baghdad. The Abbasids, presenting themselves as divine-right rulers, usher in a new era of centralized administration, cultural flourishing, and intellectual expansion, significantly influenced by Persian traditions. The Abbasid caliphs, particularly under Harun ar-Rashid (786–809) and his son Al-Mamun (813–833), preside over a remarkable cultural renaissance, with Baghdad becoming a center for philosophical, scientific, and literary achievements.

Persian Influence and Cultural Integration

Under Abbasid rule, the integration of Persian administrative practices, such as the role of vizier and the bureaucratic institution of the divan, becomes foundational. Persian scholars profoundly impact Islamic sciences, literature, medicine, and philosophy, with Arabic becoming the language of administration in 696 but Persian remaining widely spoken. The Iranian populace, initially slow to adopt Islam, gradually integrates into the Islamic community by the ninth century, significantly contributing to Islamic intellectual traditions.

Regional Shifts and Continued Instability

Despite Abbasid centralization, regional unrest persists. Iraq remains restive under Umayyad and early Abbasid rule, with notable rebellions including the Alid Revolt (762–763), which emphasizes enduring sectarian divisions. Armenia, semi-autonomous under the Bagratid dynasty from 806, continues to serve as a crucial buffer state between Muslim and Byzantine spheres. In 813, Ashot I, a Bagratid prince, consolidates power in Georgia, initiating nearly a millennium of Bagratid rule there.

Religious Developments and Legal Schools

The formation of distinct Sunni legal schools—notably those founded by Malik ibn Anas, Abu Hanifa, Al-Shafi‘i, and Ahmad ibn Hanbal—begins in earnest, shaping Islamic jurisprudence. Shia communities, particularly the Twelve Imams tradition, consolidate around revered figures such as Imam Reza, whose tomb at Mashhad becomes a significant pilgrimage site.

Economic and Social Prosperity

The Abbasids promote extensive economic development, infrastructure projects, and social welfare initiatives. Caliph Al-Walid I (705–715) builds the first major hospital in Damascus, institutes quarantine practices for leprosy patients, and initiates public works including street lighting, irrigation, and welfare programs. The Persian Gulf region experiences prosperity linked to the economic success of Baghdad, revitalizing trade networks.

By 819, the Middle East stands transformed by the profound cultural synthesis of Arab, Persian, and local traditions. This dynamic fusion shapes a vibrant civilization whose influences reverberate across the Islamic world and beyond, laying a foundation for centuries of cultural, scientific, and political achievements.

Ali had made Al Kufah his capital during his caliphate.

The transfer of power to Syria and to its capital at Damascus arouses envy among Iraqis.

The desire to regain preeminence prompts numerous rebellions in Iraq against Umayyad rule.

As a consequence, only men of unusual ability are sent to be governors of Al Basrah and Al Kufah.

One of the most able is Ziyad ibn Abihi, who is initially governor of Al Basrah and later also of Al Kufah.

Ziyad divides the residents of Al Kufah into four groups (not based on tribal affiliation) and appoints a leader for each one.

He also sends  fifty thousand Bedouin to Khorasan (in northeastern Iran), the eastern-most province of the empire, which is within the jurisdiction of Al Basrah and Al Kufah.

Yazid I, Muawiyah's son and his successor in 680, is unable to contain the opposition that his strong father had vigorously quelled.

Husayn, Ali's second son, refuses to pay homage and flees to Mecca, where he is asked to lead the Shias—mostly Iraqis—in a revolt against Yazid I.

Ubayd Allah, governor of Al Kufah, discovers the plot and sends detachments to dissuade him.

At Karbala, in Iraq, Husayn's band of two hundred men and women refuse to surrender and finally are cut down by a force of perhaps fourth thousand Umayyad troops.

Yazid I receives Husayn's head, and Husayn's death on the tenth of Muharram (October 10, 680) continues to be observed as a day of mourning for all Shias.

Ali's burial place at An Najaf, about one hundred and thirty kilometers south of Baghdad, and ...

...Husayn's at Karbala, about eighty kilometers southwest of Baghdad, are holy places of pilgrimage for Shias, many of whom feel that a pilgrimage to both sites is equal to a pilgrimage to Mecca.

The importance of these events in the history of Islam cannot be overemphasized.

They create the greatest of the Islamic schisms, between the party of Ali (the Shiat Ali, known in the West as Shias or Shiites) and the upholders of Muawiyah (the Ahl as Sunna, the People of the Sunna—those who follow Muhammad's custom and example) or the Sunnis.

The Sunnis believe they are the followers of orthodoxy.

The ascendancy of the Umayyads and the events at Karbala, in contrast, leads to a Shia Islam which, although similar to Sunni Islam in its basic tenets, maintains important doctrinal differences that have pervasive effects on the Shia world view.

Most notably, Shias viewed themselves as the opposition in Islam, the opponents of privilege and power.

They believe that after the death of Ali and the ascension of the "usurper" Umayyads to the caliphate, Islam took the wrong path; therefore, obedience to existing temporal authority is not obligatory.

Furthermore, in sacrificing his own life for a just cause, Husayn becomes the archetypal role model who inspires generations of Shias to fight for social equality and for economic justice.

Yazid ibn Muawiya had been sent in 676 with Arab reinforcements for the Siege of Constantinople.

The Muslim Arabs attack the great walled city in 676 and 677, but are once again unable to overcome the defenders’ Greek fire-augmented defense tactics.

Greek fire, first used at Constantinople to set fire to invading Muslim Arab ships, proves so effective that its formula is kept a state secret.

Presumably a mixture of flammable materials such as sulfur and pitch, with quicklime added to react with water and ignite, the Greeks normally use hand-operated pumps to project the substance onto enemy ships.

The Sufyanids have generally retained the Roman and Persian administrative bureaucracies they had inherited in the provinces; politically they are organized along Arab tribal lines, in which the caliph is chosen by his peers to become, theoretically, “first among equals,” and act on the advice of a shura, or tribal council.

Muawiyah, however, in securing during his lifetime an oath of allegiance to his son Yazid, has disregarded the traditional “election” and introduced the alien concept of hereditary succession.

For this reason, the Umayyad dynasty will sometimes be referred to as the Arab kingdom, reflecting traditional Muslim disapproval of the secular nature of the Umayyad state.

The Umayyad attacks against Constantinople from 669 to 678, while ultimately unsuccessful, have offset the secular image of the state, because they have been directed against the Christians.

Muawiyah has pacified the Arab kingdom, greatly extended its frontiers, and transformed the early Muslim patriarchy into an imperial monarchy, the Umayyad Caliphate.

Having beautified Damascus, he has developed a court to rival that of Constantinople.

At his death in 680, many of those whom Muawiyah had kept in check now rebel against his son Yazid, who is widely opposed in Syria and Mesopotamia, inaugurating what will be a series of bloody civil wars that will rend the fabric of the late Muawiyah’s Arabian Empire.