Did Islam Spread by the Sword?

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Within roughly a century of the Prophet’s ﷺ death in 632, armies fighting under the banner of Islam had conquered Syria, Egypt, Iraq, Persia, North Africa and Spain. These were military conquests, and any serious defence of Islam must begin by acknowledging them.

The further claim is that this is how the religion spread: that conquered people became Muslim because armies forced them to, and that Islam was therefore established by the sword. This concerns conversion, not simply conquest, and the two can be examined separately. Chronicles record when territory changed hands. Tax registers, biographical dictionaries and census records provide evidence for when populations changed religion. Historians have studied those records quantitatively.

A note on terms. A hadith is a report about something the Prophet ﷺ said or did. Each report is transmitted through a named chain of narrators and assessed for reliability. Sahih al-Bukhari and Sahih Muslim are the most rigorously screened collections. Jizya is the tax paid by non-Muslims under Muslim rule and is discussed separately in The Jizya. The Companions are the generation who knew the Prophet ﷺ personally.

The objection

The argument, stated in its strongest form, is as follows:

Islam expanded across much of the known world through military conquest in less than a century.
Its scripture contains direct commands to fight unbelievers, and the Prophet ﷺ personally led armies.
Populations living under Muslim rule later became Muslim.
The expansion of the empire and the spread of the faith were therefore the same process, and Islam owes its growth to violence.

The first two points are true as stated. The problem lies in the move from 3 to 4, and the historical evidence does not support it.

What conquest actually produced

The conquests represented the expansion of a state. They brought territory, tribute and political control: the usual aims of seventh-century empire, pursued by a new power against two exhausted rivals.
Conquered populations were not required to become Muslim. They had to accept Muslim political authority and pay tax. The existence of the jizya reflects this arrangement: a tax imposed on non-Muslim subjects assumes that substantial non-Muslim populations will continue to live under Muslim rule.

A state pursuing forced conversion would undermine a tax paid only by non-Muslims. The two policies work against each other. What the papyri document, century after century, is the continued collection of that tax from non-Muslim subjects.
The Prophet’s ﷺ standing instructions to army commanders make the political nature of submission clear. A commander was to offer three alternatives, of which conversion was only the first:

“When you meet your enemies who are polytheists, invite them to three courses of action… Invite them to accept Islam; if they respond to you, accept it from them and desist from fighting against them… If they refuse to accept Islam, demand from them the jizya. If they agree to pay, accept it from them and hold off your hands.” — Sahih Muslim 4521¹

The second alternative is decisive. The opposing population could retain its religion, accept Muslim rule, and pay the jizya, and this counted as a legitimate settlement, not a failed conversion. If conversion had been the objective, payment of a tax could not have satisfied it.

Conversion took centuries

The chronology of conversion is central to the question. If conquest itself made populations Muslim, conversion should rise sharply when a territory was conquered. The evidence does not show that pattern.

Richard Bulliet’s Conversion to Islam in the Medieval Period reconstructed conversion timelines from personal names in biographical dictionaries. Descendants of converts generally carried Muslim names, allowing the records to indicate when conversion occurred. For Iran, Iraq, Syria, Egypt and Spain, the results are slow S-curves extending over three to four centuries, not sudden changes at the time of conquest.²
Quantitative research on Egypt, based on tax records and later census data, places the conversion of the Coptic population across the period 641 to about 1200.³ The conquest took two years, while the transition to a Muslim majority took roughly five centuries.
Syria and Egypt still had substantial Christian populations at the end of the medieval period. Bulliet’s graphs must therefore be read as describing the people who eventually converted, not the entire population.²

A five-century transition is difficult to reconcile with systematic forced conversion. Coercive campaigns are meant to produce immediate, visible compliance. The Egyptian evidence instead records gradual change over about twenty generations, as people converted at different times and for different reasons.

The communities that are still there

A policy of systematic forced conversion should be visible in the disappearance of the communities subjected to it.

Egypt’s Copts have remained continuously present since before the conquest and are still the largest Christian community in the Middle East.
Assyrian and Syriac Christians in Iraq and Syria, Maronites in Lebanon, and Armenian communities throughout the region all predate Muslim rule and survived it.
Jewish communities lived continuously across the Muslim world from the seventh century until the mid-twentieth. Their departure belongs to the history of modern politics, not medieval Islamic law.
Zoroastrians remained in Iran, as did Hindus in India.

India provides an especially important test. Muslim dynasties ruled large parts of the subcontinent from the establishment of the Delhi Sultanate in 1206 until the end of Mughal rule in 1857. This amounted to six and a half centuries of Muslim political and military rule over a Hindu majority. At the end of that period, India was, and remains, overwhelmingly Hindu. The 2011 census records roughly 80 per cent Hindu and 14 per cent Muslim.⁴

Six and a half centuries of Muslim rule gave successive states more than enough time to impose conversion had that been their policy. Yet the subcontinent remained overwhelmingly Hindu. The Indian case therefore shows that forced conversion was neither a consistent state project nor effective enough to determine the region’s religious composition.

Where Islam spread with no conquest at all

If military conquest were the main mechanism of conversion, Islam should not have spread far beyond the reach of Muslim armies. Yet some of its largest populations developed in places without an Arab conquest.

Indonesia was never conquered by an Arab army. Islam arrived through trade, Sufi preaching, marriage and the conversion of local rulers, then spread gradually through the archipelago from around the thirteenth century. It is now home to roughly 230 million Muslims, more than any Arab state and more than the entire Middle East.⁵
Malaysia and the Malay archipelago were reached through the same commercial and scholarly networks.
West Africa encountered Islam through trans-Saharan trade, while East Africa encountered it along the Indian Ocean coast. In both regions, merchants and scholars were the main carriers rather than invading armies.
China has had Muslim communities since the Tang period, founded by traders travelling over land and sea.

Together, these regions contain a substantial share of the world’s Muslims. Any account that treats conquest as the main explanation for Islam’s spread must still explain Indonesia, whose vast Muslim population developed without an Arab conquest.

What the Qur’an says about compelling belief

The verses commonly cited in support of coercion address fighting in particular conflicts. The Qur’an also speaks directly about belief and whether it may be compelled.

Religious compulsion is rejected directly:

“Let there be no compulsion in religion” (Sūrat al-Baqarah 2:256), Dr. Mustafa Khattab, The Clear Quran

﴿لَآ إِكْرَاهَ فِى ٱلدِّينِ﴾ [سُورَةُ البَقَرَةِ: ٢٥٦]
The Prophet ﷺ is told that universal belief was not God’s will and is asked whether he could force people to believe:

“Had your Lord so willed ˹O Prophet˺, all ˹people˺ on earth would have certainly believed, every single one of them! Would you then force people to become believers” (Sūrat Yūnus 10:99), Dr. Mustafa Khattab, The Clear Quran

﴿وَلَوْ شَآءَ رَبُّكَ لَءَامَنَ مَن فِى ٱلْأَرْضِ كُلُّهُمْ جَمِيعًا ۚ أَفَأَنتَ تُكْرِهُ ٱلنَّاسَ حَتَّىٰ يَكُونُوا۟ مُؤْمِنِينَ ۝٩٩﴾ سُورَةُ يُونُسَ
The choice is stated openly, while its consequences are placed in the next life rather than this one:

“so whoever wills — let him believe; and whoever wills — let him disbelieve” (Sūrat al-Kahf 18:29), Saheeh International

﴿فَمَن شَآءَ فَلْيُؤْمِن وَمَن شَآءَ فَلْيَكْفُرْ﴾ [سُورَةُ الكَهۡفِ: ٢٩]
The Prophet’s ﷺ role is defined as reminding, with its limits made clear:

“So remind, [O Muhammad]; you are only a reminder.” (Sūrat al-Ghāshiyah 88:21), Saheeh International

﴿فَذَكِّرْ إِنَّمَآ أَنتَ مُذَكِّرٌۭ ۝٢١﴾ سُورَةُ الغَاشِيَةِ
People are to be called to Islam through wisdom and argument, not force:

“Invite ˹all˺ to the Way of your Lord with wisdom and kind advice, and only debate with them in the best manner” (Sūrat al-Naḥl 16:125), Dr. Mustafa Khattab, The Clear Quran

﴿ٱدْعُ إِلَىٰ سَبِيلِ رَبِّكَ بِٱلْحِكْمَةِ وَٱلْمَوْعِظَةِ ٱلْحَسَنَةِ﴾ [سُورَةُ النَّحۡلِ: ١٢٥]
When an enemy offers peace, the instruction is to accept it:

“If the enemy is inclined towards peace, make peace with them. And put your trust in Allah.” (Sūrat al-Anfāl 8:61), Dr. Mustafa Khattab, The Clear Quran

﴿وَإِن جَنَحُوا۟ لِلسَّلْمِ فَٱجْنَحْ لَهَا وَتَوَكَّلْ عَلَى ٱللَّهِ﴾ [سُورَةُ الأَنفَالِ: ٦١]
Fighting is restricted to those who fight first, and limits are imposed on it:

“Fight in the cause of Allah ˹only˺ against those who wage war against you, but do not exceed the limits. Allah does not like transgressors” (Sūrat al-Baqarah 2:190), Dr. Mustafa Khattab, The Clear Quran

﴿وَقَٰتِلُوا۟ فِى سَبِيلِ ٱللَّهِ ٱلَّذِينَ يُقَٰتِلُونَكُمْ وَلَا تَعْتَدُوٓا۟ ۚ إِنَّ ٱللَّهَ لَا يُحِبُّ ٱلْمُعْتَدِينَ ۝١٩٠﴾ سُورَةُ البَقَرَةِ

The rules the armies were given

A policy of conversion by force would require rules of war that allow civilians to be terrorised. The recorded instructions instead distinguish between those who fight and those who do not.

One incident prompted an explicit prohibition on killing non-combatants:

“During some of the expeditions of Allah’s Messenger ﷺ a woman was found killed, so Allah’s Messenger ﷺ forbade the killing of women and children.” — Sahih al-Bukhari 3015; also Sahih al-Bukhari 3014, Sahih Muslim 4547–4548, and Muwatta Malik 967⁶
Another report states the reason and records the order being sent to Khalid ibn al-Walid, one of the most prominent Muslim commanders. Hanzala al-Katib describes the Prophet ﷺ finding soldiers gathered around the body of a woman:

“This one was not among those who were fighting.” Then he said to a man: “Go to Khalid ibn al-Walid and tell him that the Messenger of Allah ﷺ commands you: do not kill any children, or women, or any labourer.” — Sunan Ibn Majah 2842, graded hasan sahih⁷

The relevant distinction is between combatants and non-combatants, not Muslims and non-Muslims. The report does not mention the woman’s religion because it makes no difference to the ruling. She was protected because she was not fighting, and the labourer is included for the same reason.
The standing instructions to commanders also prohibit treachery, mutilation, looting and the killing of children.¹
Abu Bakr, the Prophet’s ﷺ closest companion and the first caliph after his death, gave the armies sent to Syria a broader set of instructions: do not kill women, children, the elderly or the infirm; do not cut down fruit trees or destroy inhabited places; do not slaughter livestock except for food; and leave monks in their monasteries alone.

Muwatta Malik 968. Its chain is graded weak, and the report records a Companion’s instruction rather than a ruling of the Prophet ﷺ. It is cited here only as widely transmitted evidence of early practice, not as proof of the legal rule. That proof comes from the Prophetic reports above.⁸

Where the criticism does land

Islam should be judged by its authoritative teachings rather than by every act committed in its name. That distinction also requires acknowledging cases in which Muslims did impose conversion by force.

The Almohads in twelfth-century North Africa and Spain forced Jews and Christians to convert under threat of death or exile. Their policy ended communities that had survived four centuries of earlier Muslim rule, and Maimonides’ family fled the Almohads.⁹
The Safavids used state coercion from 1501 onward to convert Iran from Sunni to Twelver Shi’i Islam. This was a case of Muslims forcibly converting other Muslims.⁹
Aurangzeb’s temple demolitions and restoration of the jizya in Mughal India in 1679 were coercive policies and were resisted as such.

None of these cases is defensible, and none is being defended here. They were not, however, the mechanism that produced the Muslim world. They are identifiable episodes within a longer history in which non-Muslim communities usually survived for centuries. The Almohad policy is notable precisely because it departed from that broader pattern.

The strongest remaining objection

The strongest remaining criticism accepts that conquest did not usually produce immediate conversion but shifts attention to the conditions created by Muslim rule. The conquests may not have converted people directly, but they made conversion advantageous through taxation, limits on advancement and access to a ruling class defined by religion. On this account, “not by the sword” remains a technical distinction because military rule created the incentives.

This objection should be answered directly.

The tax incentive was real, including its measurable effect on the poorest converts. The quantitative evidence is discussed in detail in The Jizya.
Incentive is not the same as force. The distinction matters because the original accusation presents Islam as uniquely dependent on violence. Expanding powers throughout history have made their own religion socially advantageous. If social advantage is the charge, it is no longer specific to Islam.
The timescale still requires explanation. An advantage that operates for five centuries without producing a majority is limited in effect. The Egyptian evidence shows a slow, partial and reversible process rather than a population acting under compulsion.
It also explains nothing outside the empire. Indonesia experienced no Muslim conquest, had no jizya and had no Muslim ruling class to join, yet became the largest Muslim country in the world.

Conclusion

The Arab conquests were real, rapid and military. Islam’s expansion as a political power depended heavily on them. The evidence does not show that Islam’s expansion as a faith followed in the same way.

The populations conquered by Muslim armies remained largely non-Muslim for centuries. Many of the communities placed under Muslim rule still exist. The largest Muslim population in the world developed without Muslim conquest, and the Qur’an rejects compelled belief while defining the Prophet’s ﷺ task as reminding. Cases of forced conversion did occur, but they are identifiable episodes that conflict with both the cited sources and the broader historical pattern.

The empire expanded through conquest. The evidence shows that the religion usually spread through other means.