Short answer
No. Muslim states did expand by conquest, as empires did then, but Islam forbids forcing anyone to convert. In the conquered lands Christians and Jews kept their faith, and people became Muslim slowly over centuries. Many of the largest Muslim populations today, such as Indonesia, received Islam with no army at all.
Islamic law, Hanafi and the other schools, holds that 'there is no compulsion in religion' (2:256). Hanafi law accepts jizya from the People of the Book and from non-Arab polytheists and leaves them their religion; the special rule for the idolaters of Arabia in the Prophet's ﷺ time is a separate discussion.
Other madhhabs
- Shafi'i
- Jizya is accepted only from Jews, Christians and Magians (Zoroastrians), not from other polytheists.
- Maliki
- Jizya may be accepted from any non-Muslim, including polytheists.
- Hanbali
- In the relied-upon view, jizya is accepted only from the People of the Book and the Magians.
Explanation
It helps to separate two things. Conquest is about who governs a land. Conversion is about what is in a person's heart. The early Muslim state fought the Byzantine and Persian empires and took their lands, as states of that age did. But the Quran says "There shall be no compulsion in religion", and Islamic law protected the religion of non-Muslims living under Muslim rule.
History shows this. Egypt, Syria and Iraq came under Muslim rule in the 630s and 640s, but historians agree that their populations became mostly Muslim only over several centuries. Christian churches and Jewish communities continued, and still exist in those lands. Under Muslim rule in Spain and the Ottoman lands, Jews and Christians kept their faith for centuries.
Many regions became Muslim without conquest at all: Indonesia and Malaysia, much of West and East Africa, the Maldives and parts of China. Merchants, scholars and Sufi teachers carried Islam there. Indonesia is now the country with the largest Muslim population in the world.
The aim of the Prophet's ﷺ mission was guidance, not killing. At Khaybar he told Ali to invite people to Islam first, and said that Allah guiding one person through him was better than the finest red camels. Muslims believe in calling with wisdom and good example. See How did Islam spread in Indonesia? and How did Islam spread in West Africa?
The evidence
Quran, Surah Al-Baqara 2:256
لَآ إِكْرَاهَ فِى ٱلدِّينِ ۖ قَد تَّبَيَّنَ ٱلرُّشْدُ مِنَ ٱلْغَىِّ ۚ فَمَن يَكْفُرْ بِٱلطَّٰغُوتِ وَيُؤْمِنۢ بِٱللَّهِ فَقَدِ ٱسْتَمْسَكَ بِٱلْعُرْوَةِ ٱلْوُثْقَىٰ لَا ٱنفِصَامَ لَهَا ۗ وَٱللَّهُ سَمِيعٌ عَلِيمٌ ﴿٢٥٦﴾
There shall be no compulsion in [acceptance of] the religion. The right course has become clear from the wrong. So whoever disbelieves in Taghut and believes in Allah has grasped the most trustworthy handhold with no break in it. And Allah is Hearing and Knowing.
Faith cannot be forced.
Quran, Surah Al-Mumtahana 60:8
لَّا يَنْهَىٰكُمُ ٱللَّهُ عَنِ ٱلَّذِينَ لَمْ يُقَٰتِلُوكُمْ فِى ٱلدِّينِ وَلَمْ يُخْرِجُوكُم مِّن دِيَٰرِكُمْ أَن تَبَرُّوهُمْ وَتُقْسِطُوٓا۟ إِلَيْهِمْ ۚ إِنَّ ٱللَّهَ يُحِبُّ ٱلْمُقْسِطِينَ ﴿٨﴾
Allah does not forbid you from those who do not fight you because of religion and do not expel you from your homes - from being righteous toward them and acting justly toward them. Indeed, Allah loves those who act justly.
Justice and kindness to peaceful non-Muslims.
Quran, Surah An-Nahl 16:125
ٱدْعُ إِلَىٰ سَبِيلِ رَبِّكَ بِٱلْحِكْمَةِ وَٱلْمَوْعِظَةِ ٱلْحَسَنَةِ ۖ وَجَٰدِلْهُم بِٱلَّتِى هِىَ أَحْسَنُ ۚ إِنَّ رَبَّكَ هُوَ أَعْلَمُ بِمَن ضَلَّ عَن سَبِيلِهِۦ ۖ وَهُوَ أَعْلَمُ بِٱلْمُهْتَدِينَ ﴿١٢٥﴾
Invite to the way of your Lord with wisdom and good instruction, and argue with them in a way that is best. Indeed, your Lord is most knowing of who has strayed from His way, and He is most knowing of who is [rightly] guided.
The way of calling to Islam.
Sahih al-Bukhari 3701
Sahih... لأن يهدي الله بك رجلا واحدا خير لك من أن يكون لك حمر النعم ...
"That Allah guides one man through you is better for you than red camels."
The goal was guidance, not conquest.
Where the ruling is recorded
- al-Hidaya (al-Marghinani), Kitab al-Siyar, chapter on jizya. The Hanafi rules protecting the religion of People of the Book under Muslim rule.
- Futuh al-Buldan (al-Baladhuri), Chapters on the treaties with the people of Syria and Egypt. Records the treaties that left churches and religion in place.
- Ahkam al-Quran (al-Jassas), Commentary on 2:256. A Hanafi reading of the verse on no compulsion.
This answer is pending review by the scholars on our team. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.