The Rise of Islam

Summary

This chapter treats the formation, institutional development, and intellectual flourishing of the Islamic world as a self-contained arc. It covers the origins of Islam (Muhammad, the Quran, the Hijra, the Five Pillars), the early caliphates (Rashidun, Umayyad, Abbasid) and the Sunni–Shia split, the Baghdad House of Wisdom, the Islamic Golden Age, dar al-Islam as a scholarly and trade space spanning three continents, and the development of Sufism. The Islamic-civilization arc set up here is a prerequisite for trans-Saharan trade, Indian Ocean trade, and the Eve-of-Integration chapter.

Concepts Covered

This chapter covers the following 13 concepts from the learning graph:

Origins Of Islam
Muhammad
Quran
Hijra
Five Pillars Of Islam
Sunni-Shia Split
Rashidun Caliphate
Umayyad Caliphate
Abbasid Caliphate
Baghdad House Of Wisdom
Islamic Golden Age
Dar Al-Islam
Sufism

Prerequisites

This chapter builds on concepts from:

From an Arabian merchant city to three continents in a hundred years.

Chronos waves alongside a small Quranic page and a star-and-crescent Welcome back. The Late Antiquity of Chapter 12 ended with a Byzantine and Sasanian world weakened by climate, plague, and recurrent warfare. This chapter picks up in early seventh-century Arabia with a young merchant in the city of Mecca, and follows the religious, political, and intellectual transformation that — within a century — will reshape the Mediterranean, Iran, and a great deal of Asia. Pull up a coffee cup and a copy of the Quran.

Pre-Islamic Arabia: The Setting

Before turning to Muhammad and the Quran, a sketch of the pre-Islamic Arabian context is essential. The Arabian Peninsula in the 6th century CE was inhabited by Arab tribes organized along genealogical (clan and tribal) lines, with both sedentary populations in oasis cities (Mecca, Medina, Ta'if) and along the coasts and nomadic Bedouin populations across the interior deserts. Arabian society was deeply tribal, with strong codes of hospitality, vendetta, honor, and tribal solidarity ('asabiyya).

Religiously, pre-Islamic Arabia was diverse. Most Arabs practiced polytheism, venerating local gods and goddesses, with a high god (Allah, "the God") often acknowledged as creator. Christianity had penetrated the peninsula at multiple points (the Christian kingdom of Najran in the south; Christian Arab tribes in the north under Byzantine influence). Judaism was present in both Yemen (where the kingdom of Himyar had become Jewish in the early 6th century) and the Hijaz (with substantial Jewish communities in Medina and elsewhere). A monotheistic seeking-tradition known to later Islamic sources as the hanifs (Arabic hanif, "true monotheist") rejected polytheism while not adopting Judaism or Christianity. The religious landscape was, in short, complex and conducive to monotheistic synthesis.

The most important city for this chapter's story is Mecca, an oasis trading center in the western Hijaz region of Arabia. Mecca lay along the trade route connecting South Arabia (with its frankincense and Indian Ocean imports) to Roman/Byzantine Syria, and was governed by the Quraysh tribal confederation that had assembled an elite role as caravan organizers, bankers, and protectors of trade. The Kaaba — a cubic sanctuary at the center of Mecca — housed images of multiple Arabian deities and was a major pilgrimage site that brought religious-economic prestige to the Quraysh.

Muhammad and the Quran

Muhammad ibn Abdullah (~570–632 CE) was born into a relatively poor branch of the Quraysh tribe. Orphaned young, raised by his uncle Abu Talib, and apprenticed in the caravan trade, he developed a reputation as al-Amin, "the trustworthy." He married Khadija, an older Meccan widow and merchant for whom he worked, and lived a quiet middle-class life until approximately the year 610 CE, when — according to Islamic tradition — he received the first revelation from the angel Jibril (Gabriel) on Mount Hira outside Mecca: "Recite (iqra') in the name of your Lord who created..." (Quran 96:1). Over the next 22 years, Muhammad would receive revelations that he and his community understood as the direct word of Allah, eventually compiled as the Quran ("the Recitation").

The Quran is roughly the length of the New Testament, divided into 114 chapters (suras) of varying length, ordered (from sura 2 onward) by length rather than chronologically. The Quran's central themes include strict monotheism (tawhid: God is one, with no partners or offspring), ethical responsibility to family, community, the poor, orphans, and widows, resurrection and divine judgment at the end of time, and a prophetic lineage running from Adam through Noah, Abraham, Moses, David, and Jesus to Muhammad as the "Seal of the Prophets" (Quran 33:40). The Quran explicitly recognizes Christians and Jews as People of the Book (ahl al-kitab) — communities who had received earlier divine revelations — even as it argues that the message had been distorted in transmission and was now being restored. Quranic Arabic, with its rhythmic prose, vivid imagery, and rhetorical structure, became the linguistic standard against which classical Arabic would be measured for centuries.

Muhammad's preaching in Mecca (~610–622 CE) drew a small but committed following — including his wife Khadija, his cousin Ali, his close friend Abu Bakr, and others — but provoked strong opposition from the Quraysh elite, whose religious-economic system Muhammad's monotheistic message threatened. After roughly twelve years of increasingly hostile Meccan resistance, Muhammad and his followers accepted an invitation from the people of Yathrib (a city ~340 km north of Mecca) to migrate there and serve as community arbiters. The migration of 622 CE is called the Hijra ("emigration"); the Islamic calendar dates from this year (so Muslim sources will write "1 AH" for "year 1 of the Hijra"). Yathrib was renamed Medina ("the City," short for Madinat al-Nabi, "the City of the Prophet").

In Medina, Muhammad served as both religious teacher and political leader. He drafted a foundational document (the Constitution of Medina) establishing the umma — the community of believers — as a political-religious entity that included Muslims, Jews, and other groups under shared obligations. Over the next decade, the Medinan community grew, fought a series of military and diplomatic conflicts with Mecca and surrounding tribes, and ultimately negotiated the peaceful submission of Mecca itself (630 CE), at which point Muhammad cleansed the Kaaba of its polytheist images and rededicated it to Allah. By Muhammad's death in 632 CE, most of the Arabian Peninsula had accepted his religious-political leadership.

The Five Pillars of Islam

The core practices of Islam are summarized as the Five Pillars (arkan al-Islam), which structure the religious obligations of every Muslim.

Pillar	Arabic	Practice
1. Declaration of Faith	Shahada	"There is no god but God; Muhammad is the Messenger of God."
2. Daily Prayer	Salat	Five prayers per day, performed at prescribed times facing Mecca.
3. Almsgiving	Zakat	An obligatory charitable contribution (typically 2.5%) from wealth above a basic threshold.
4. Fasting	Sawm	Fasting from dawn to sunset during the lunar month of Ramadan.
5. Pilgrimage	Hajj	A pilgrimage to Mecca, required at least once in a Muslim's lifetime if physically and financially able.

The Five Pillars combine individual devotion (the daily salat, the Ramadan fast) with community obligation (zakat for the poor, hajj as a continent-spanning communal gathering). They are public in a way that distinguishes Islamic practice from more privatized contemporary religious models: salat happens visibly throughout the day; Ramadan transforms the rhythm of the entire community; the hajj brings millions of Muslims from across the world to Mecca every year, producing one of the largest annual gatherings of human beings on Earth. The Pillars are also simple and portable — they require no formal ordained clergy, no architectural infrastructure beyond a clean space and the direction of Mecca, and no membership in any specific institution. This portability is one of the structural reasons Islam was able to spread effectively across diverse cultural and political contexts.

The Rashidun and the Sunni–Shia Split

Muhammad died in 632 CE without a clearly designated successor. The crisis of succession is the seed of the most significant division in Islamic history. The community in Medina elected Abu Bakr — Muhammad's close friend and father-in-law — as the first Caliph (khalifa, "successor"). Abu Bakr served two years before being succeeded by Umar ibn al-Khattab (r. 634–644 CE), then Uthman ibn Affan (r. 644–656 CE), and finally Ali ibn Abi Talib (r. 656–661 CE), Muhammad's cousin and son-in-law. The four are known collectively in Sunni tradition as the Rashidun ("rightly-guided") Caliphs.

Under the Rashidun, the Muslim community expanded astonishingly fast. Within roughly 20 years of Muhammad's death, Muslim armies had conquered:

Sasanian Iran (largely complete by 651 CE), ending the Persian Empire that had been Rome's rival for four centuries.
Byzantine Syria, Palestine, Egypt, and parts of North Africa (632–642 CE).
Significant parts of the Caucasus and Central Asia.

The speed and scale of these conquests is remarkable and has been the subject of extensive analysis. Several factors contributed:

The Byzantine and Sasanian empires were exhausted by their long mutual wars (especially 602–628 CE) and by the demographic shock of the Justinianic Plague and Late Antique Little Ice Age discussed in Chapter 12.
Local populations — Christians, Jews, and Zoroastrians in the conquered territories — were often indifferent or even welcoming to Arab rule, which initially imposed lighter taxes and permitted continued religious practice under the dhimmi status (a protected minority status with specific tax obligations and legal restrictions).
Arab armies were highly mobile, motivated, and tactically effective.
The newly established Caliphate provided a unified political-religious framework capable of coordinating military operations across vast distances.

Conversion of the conquered populations to Islam was gradual — taking centuries in most regions — and was driven less by coercion than by the practical and social advantages of joining the dominant religious community.

The succession crisis came to a head with Ali. Ali, Muhammad's cousin and son-in-law (married to his daughter Fatima), had supporters who believed he should have been the first caliph. When he became the fourth caliph in 656 CE after Uthman's assassination, his rule was contested by the relatives of Uthman, especially Mu'awiya, the governor of Syria. Civil war (the First Fitna) ensued. Ali was assassinated in 661 CE by a Kharijite (a member of a faction that had originally supported Ali but turned against him). Mu'awiya succeeded him as caliph and founded the Umayyad dynasty.

Ali's supporters — the Shi'a ("partisans," from Shi'at Ali, "the party of Ali") — never accepted the legitimacy of the Umayyad succession. They held that leadership of the Muslim community properly belonged to Ali's lineage through Fatima, and that authoritative interpretation of the religion required descent from the Prophet through this line of Imams. The crisis was sharpened by the Battle of Karbala (680 CE), where Ali's son Husayn and his small party were killed by Umayyad forces — a martyrdom event that became foundational for Shi'a identity and is commemorated annually in the rituals of Ashura.

The eventual division between Sunnis (~85% of Muslims globally today) and Shi'as (~15%, concentrated in Iran, southern Iraq, parts of Lebanon and Bahrain, and the Indo-Iranian borderlands) involves more than just the succession question. Sunnis recognize the legitimacy of all four Rashidun caliphs and the consensus (ijma) of the early community as a source of authority alongside the Quran and the hadith (sayings of the Prophet). Shi'as emphasize the special religious-political authority of Ali's lineage through twelve (in the dominant Twelver branch) or seven (in the Ismaili branch) Imams. The two traditions also developed distinct ritual practices, legal schools, and theological emphases, while sharing the core of monotheistic faith, the Quran, and the Five Pillars.

Question	Sunni Position	Shi'a Position
First caliph	Abu Bakr, by community consensus	Ali, by Prophetic designation
Source of authority	Quran, Sunna, consensus, analogical reasoning	Quran, teachings of the Imams
Religious leadership today	Scholars (ulama) interpreting tradition	Imam (in occultation, awaiting return); senior clerics interpret in his absence
Legal schools	Hanafi, Maliki, Shafi'i, Hanbali (the four major Sunni madhhabs)	Ja'fari (Twelver) and others

The Umayyad Caliphate (661–750 CE)

The Umayyad Caliphate, ruled from Damascus in Syria, expanded the Islamic state to its largest territorial extent. By the early 8th century CE, the Umayyads ruled from the Iberian Peninsula (conquered 711 CE) across North Africa, through Egypt and the Levant, across Mesopotamia, Iran, and Central Asia, into the Indus Valley (711 CE). The empire spanned ~13 million km² and contained perhaps 40 million subjects — the largest single political unit in the world at the time.

The Umayyads ran a politically and culturally Arab-centric empire. Arab Muslims held a privileged tax status; non-Arab converts to Islam (mawali) were treated as second-class even within the Muslim community; and Arab tribal politics dominated court culture. Administratively, the Umayyads inherited the bureaucratic structures of the Byzantines (in Syria and Egypt) and the Sasanians (in Iran), gradually translating administrative documents from Greek and Pahlavi into Arabic over the late 7th and 8th centuries. Arab identity as cultural-political category — and Arabic as administrative lingua franca — coalesced under the Umayyads.

Despite the territorial success, Umayyad legitimacy was contested. Shi'a opposition continued; Kharijite and other dissident movements appeared; and many non-Arab Muslims resented the mawali system. A coalition of these dissatisfied groups — coordinated by the Abbasid family, distant relatives of Muhammad — overthrew the Umayyads in 750 CE in a revolution that began in eastern Iran and spread west. The Abbasids massacred most of the Umayyad family at a notorious banquet, but one young prince — Abd al-Rahman I — escaped to Spain and founded a separate Umayyad state at Córdoba that would persist until 1031 CE and be one of the great cultural centers of medieval Europe.

The Abbasid Caliphate and the Islamic Golden Age

The Abbasid Caliphate (750–1258 CE in formal title; effective central control much shorter) inaugurated a strikingly different style of rule. The Abbasids:

Moved the capital from Damascus to a new city on the Tigris — Baghdad, founded in 762 CE under Caliph al-Mansur. Baghdad was a planned circular city ("the Round City") at the center of the world's most fertile agricultural region and at the crossroads of trade routes from Iran, India, and the Mediterranean.
Decentered Arab privilege, integrating non-Arab Muslims (especially Persians) into the highest reaches of the bureaucracy and the cultural elite. Persian administrative traditions, court etiquette, literary aesthetics, and political theory profoundly shaped Abbasid culture.
Patronized scholarship at unprecedented levels. The cultural center of gravity of the Islamic world shifted decisively toward the Persian-Arab synthesis that would define medieval Islamic civilization.

Under the early Abbasids — especially Caliph Harun al-Rashid (r. 786–809 CE) and his son al-Ma'mun (r. 813–833 CE) — Baghdad became the wealthiest and most cosmopolitan city in the western half of Eurasia. Al-Ma'mun systematized state-sponsored scholarship through what later came to be called the Bayt al-Hikma ("House of Wisdom"), which functioned as a translation institute, library, and research center. The Baghdad House of Wisdom organized the systematic translation of Greek, Persian, Indian, and Syriac scientific and philosophical works into Arabic, paying translators in gold (reportedly by the weight of the translated manuscript). Within roughly two centuries, the bulk of surviving classical Greek scientific and philosophical literature had been translated into Arabic — in many cases preserving texts whose Greek originals would later be lost.

This translation movement was the foundation of the Islamic Golden Age (~800–1200 CE), an era of extraordinary scholarly achievement across the Islamic world. Highlights include:

Mathematics. Al-Khwarizmi (~780–850 CE) systematized algebra (the word algebra comes from his treatise Al-Jabr) and introduced Hindu-Arabic numerals to the Islamic world; his name is the origin of the word algorithm. Omar Khayyam (1048–1131 CE) developed methods for solving cubic equations and made important contributions to the theory of parallels.
Astronomy. Al-Battani (~858–929 CE), al-Tusi (1201–1274 CE), and others produced star catalogs, refined trigonometric methods, and developed astronomical instruments and observatories that were studied across Eurasia. The names of many bright stars in modern English (Aldebaran, Algol, Betelgeuse, Vega, Altair, Deneb) are Arabic.
Medicine. Al-Razi (Rhazes, 854–925 CE) wrote major works on smallpox, measles, and clinical medicine. Ibn Sina (Avicenna, 980–1037 CE) produced The Canon of Medicine, a five-volume synthesis that remained a standard medical textbook in European universities through the 17th century.
Philosophy. Al-Farabi (~872–950 CE), Ibn Sina, Al-Ghazali (1058–1111 CE), and Ibn Rushd (Averroes, 1126–1198 CE) elaborated the integration and critique of Greek philosophy (especially Aristotle and Neoplatonism) within an Islamic theological framework. Ibn Rushd's commentaries on Aristotle were so influential in medieval Latin Christendom that he was simply called "the Commentator."
History and Geography. Al-Biruni (973–1048 CE) wrote pioneering comparative studies of Indian religion, mathematics, and culture; Ibn Battuta (1304–1368 CE) traveled across most of dar al-Islam and produced a famous travel narrative.
Optics. Ibn al-Haytham (Alhazen, ~965–1040 CE) wrote the Book of Optics, establishing the experimental method in optical research and producing results that anticipated Kepler and Newton.

The Islamic Golden Age preserved, extended, and synthesized the intellectual traditions of the classical Mediterranean, Iran, India, and Central Asia. Many of the foundations of later European mathematics, astronomy, medicine, and philosophy were transmitted to the medieval Latin West through translations from Arabic — often via Spain and Sicily — beginning in the 11th and 12th centuries. The European "Renaissance" of the 14th century onward owes substantial debts to this earlier Islamic synthesis.

Dar al-Islam: A Three-Continent Scholarly and Trade Space

The phrase Dar al-Islam ("the abode of Islam") refers to the integrated cultural-political space of Muslim-majority territories, which by the 9th–10th centuries spanned three continents: from Spain (al-Andalus) and Morocco in the west, through North Africa, Egypt, the Levant, the Arabian Peninsula, Mesopotamia, Iran, Central Asia, and into the Indus Valley. Dar al-Islam was not a single political unit — by the 9th century it had broken into multiple independent caliphates, sultanates, and emirates — but it was a single cultural-religious space, bound together by:

Arabic as the language of the Quran, religious scholarship, and (for a long period) science and administration.
Islamic law (sharia) with regional variations within the four major Sunni schools (Hanafi, Maliki, Shafi'i, Hanbali) and the Shi'a Ja'fari school.
The annual hajj that brought Muslims from across the dar al-Islam to Mecca and back, carrying with them news, ideas, manuscripts, and commercial relationships.
Long-distance trade networks — across the Sahara to West Africa, across the Indian Ocean to East Africa, India, Southeast Asia, and Tang China, across the Silk Road to Central Asia and beyond — with Muslim merchant communities along their length.
A shared scholarly culture in which a scholar trained in Córdoba could reasonably expect to find common reference points with a scholar in Baghdad or Bukhara, and to circulate works through the same manuscript economy.

Dar al-Islam was, by the year 1000 CE, the most economically integrated and intellectually vibrant region of the Eastern Hemisphere. We will pick up its connections to West Africa (trans-Saharan trade), East Africa (Swahili coast), and South and Southeast Asia (Indian Ocean trade) in Chapter 15.

Diagram: Dar al-Islam in the 10th Century CE

Dar al-Islam ~1000 CE — interactive map

Type: map sim-id: dar-al-islam-1000-ce-map
Library: Leaflet
Status: Specified

Learning objective (Bloom: Understanding/Analyzing): The student can locate the political subdivisions of dar al-Islam ~1000 CE (Abbasid Caliphate at Baghdad, Fatimid Caliphate in Egypt and North Africa, Umayyad Caliphate of Córdoba in Spain, Samanid Empire in Central Asia, Ghaznavid Empire pushing into northern India), trace the major trade routes, and identify the cultural unity that persisted across political fragmentation.

Visual structure. A map of the eastern hemisphere ~1000 CE with major Muslim polities shaded distinctly: Abbasid Caliphate (red), Fatimid Caliphate (green), Umayyad Caliphate of Córdoba (blue), Samanid Empire (purple), Ghaznavid Empire (orange). Major trade routes overlaid: trans-Saharan caravan routes (gold), Indian Ocean shipping lanes (teal), Silk Road through Central Asia (brown), Volga-Caspian fur route (gray). Key cities flagged with their populations, founding dates, and major institutions: Baghdad, Cairo, Córdoba, Bukhara, Samarkand, Kairouan, Damascus, Cordoba, Mecca, Medina.

Interactivity. (1) Hover a polity for ruler ~1000 CE, capital, religious orientation (Sunni / Shi'a / Ismaili), and major sites. (2) Click a trade route to see typical goods and documented merchant communities. (3) Toggle "scholarly network" — overlays the migration paths of major Golden Age scholars (al-Khwarizmi, Avicenna, Averroes, al-Biruni) showing how they moved across political boundaries. (4) Toggle "Eastern Christendom" — overlays the Byzantine Empire, the Coptic and Ethiopian Christian communities, and the Christian kingdoms of Nubia for context.

Default layout. Responsive Leaflet map at 1000 CE coastline; minimum height 600 px. Polity overlays as semi-transparent shaded polygons.

Color palette. As above; cities marked with circular icons sized by population.

Implementation: Leaflet with GeoJSON polity polygons and overlay polylines; data in data.json. Deploy at docs/sims/dar-al-islam-1000-ce-map/.

Sufism: The Mystical Tradition

Alongside the formal scholarly and legal traditions, Islam developed a rich mystical tradition known as Sufism (Arabic tasawwuf). Sufism is the interior, devotional, experiential dimension of Islam, oriented toward direct knowledge of God through love, contemplation, and disciplined practice. The name sufi probably derives from suf, the Arabic word for the rough wool garments worn by early ascetics.

Sufism developed through the early Abbasid period (8th–9th centuries) and matured into organized traditions by the 10th–13th centuries. Major figures include:

Rabi'a al-Adawiyya (~717–801 CE) — an early female Sufi mystic of Basra, articulating love of God as the highest motive of religious practice.
Al-Hallaj (~858–922 CE) — a Persian mystic who was executed in Baghdad for the ecstatic utterance "I am the Truth" (which orthodox jurists read as a claim of divinity, while later Sufi tradition read as a description of mystical union).
Al-Ghazali (1058–1111 CE) — a major Sunni theologian and jurist whose mid-life turn toward Sufism integrated mysticism into mainstream Sunni piety; his Revival of the Religious Sciences (Ihya 'Ulum al-Din) is one of the most influential works in Islamic religious literature.
Ibn Arabi (1165–1240 CE) — a Spanish-born Sufi metaphysician whose voluminous writings articulated the doctrine of the "unity of being" (wahdat al-wujud).
Jalal al-Din Rumi (1207–1273 CE) — a Persian-language Sufi poet whose Mathnawi is one of the most read poetic works in the Persian-speaking world and whose verses (in many translations) are widely loved today.

Sufism also developed institutionally through Sufi orders (tariqa, "path") — networks of teachers and disciples organized around lineages of spiritual authority. Major orders (Qadiriyya, Naqshbandiyya, Mevleviyya, Chishti, Shadhili) developed distinct practices (specific dhikr recitations, meditation methods, sometimes music or dance) and spread along the trade routes, often serving as the primary vehicle for the spread of Islam to non-Arab populations in West Africa, sub-Saharan Africa, India, Central Asia, Anatolia, and Southeast Asia. Many converted populations encountered Islam first through a wandering Sufi teacher, not through a conqueror's army.

Religion is rarely just one thing.

Chronos points to a small Quranic page and a Sufi rosary Modern public discourse often presents Islam — like Christianity, like Judaism, like Buddhism — as a single block with one set of beliefs and practices. The actual historical Islam contains the legal sophistication of the four Sunni madhhabs, the Imam-centered authority of Shi'a tradition, the philosophical synthesis of Avicenna and Averroes, the medical encyclopedism of al-Razi, the mystical poetry of Rumi, and the everyday devotion of millions of believers across three continents and 1,400 years. The same internal diversity is true of every major religious tradition. When you encounter a confident sentence like "Muslims believe..." or "Christians teach...", ask which Muslims or which Christians, in which century, and in which region. This is bias and misinformation detection applied to religion — a domain where it is especially important.

Putting the Rise of Islam in Frame

By approximately 1000 CE, the Islamic world was the most economically integrated and intellectually vibrant region in the eastern hemisphere. The political unity of the early Caliphate had given way to multiple successor states (Abbasid, Fatimid, Umayyad of Córdoba, Samanid, Ghaznavid, and others), but the cultural-religious unity of dar al-Islam persisted across them. The translation movement of the 9th century had preserved much of classical Greek learning while producing original work in mathematics, astronomy, medicine, philosophy, and optics. Sufism was beginning the institutional development that would carry Islam to populations far beyond the early Arab conquests. The intellectual and economic relationships between dar al-Islam and the rest of the Eastern Hemisphere — sub-Saharan Africa, India, China, the Christian West — were the engines of the post-classical commercial and intellectual networks that the next chapters will continue to trace.

Pre-Islamic Arabia was tribal, religiously diverse, and commercially networked, with monotheistic seekers (hanifs) alongside polytheists, Jews, and Christians.
Muhammad (~570–632 CE) preached strict monotheism in Mecca, migrated to Medina (the Hijra, 622 CE), and established a religious-political community that, within a decade, had unified most of Arabia.
The Quran is the central scripture; the Five Pillars structure individual and communal religious obligations.
The Rashidun Caliphate (632–661 CE) presided over rapid conquest; the Sunni–Shia split crystallized in the disputes over leadership and the martyrdom of Husayn at Karbala (680 CE).
The Umayyad Caliphate (661–750 CE) extended Islamic rule from Spain to the Indus, run from Damascus.
The Abbasid Caliphate (from 750 CE) shifted the center to Baghdad, integrated Persian elites, and patronized the Baghdad House of Wisdom and the Islamic Golden Age — the translation, preservation, and extension of classical Greek and Indian science, mathematics, medicine, and philosophy.
Dar al-Islam by 1000 CE was a three-continent scholarly and commercial space bound together by Arabic, sharia, hajj, trade, and shared scholarship even where political unity had fractured.
Sufism developed as the mystical-devotional tradition; Sufi orders were the primary vehicle for the spread of Islam to non-Arab populations along the trade routes.

You can read across the Islamic world.

Chronos beams quietly with a small calligraphic flourish From a young merchant on Mount Hira to Avicenna's Canon of Medicine to Rumi's poetry — you have followed the formation, expansion, and intellectual flowering of one of the largest civilizational arcs in history. You also have the analytical posture to read confidently inside the diversity of dar al-Islam without flattening Sunnis, Shi'as, Sufis, philosophers, lawyers, and merchants into a single block. Onward — to the post-classical world's other major centers: Tang and Song China, Carolingian Europe, and the trans-continental networks they wove together.