It is a common misconception by some non-Muslims that Islam would not have millions of followers around the world if it had not been spread by force.
The following points will make it clear that it was the inherent power of truth, reason and logic that was responsible for the rapid spread of Islam.
Islam has always shown respect and freedom towards all other religions and views. Religious freedom is prescribed in the Quran itself:
“There is no compulsion in belief. The right way is now clearly recognizable compared to the wrong one. ” (Quran 2: 256)
This was noticed by historian De Lacy O’Leary, who wrote:  “History makes it clear, however, that the legend of the fanatical Muslims who sweep the world and use their swords to force the races subjected to Islam to accept them is one of the most fantastic, absurd myths that historians have ever repeated. ”
The famous historian, Thomas Carlyle, in his book Heroes and Hero worship, referring to this misunderstanding about the spread of Islam: “The sword, indeed, but where will you get your sword from? Every new opinion and its starting point in a minority of an individual; alone in a person’s head. She lingers there. A man alone believes she is a man against all other men. Then he takes the sword and tries to spread it, that won’t help him much. You have to grab your sword! Overall, one thing will spread itself if it can. ”
If Islam had been spread with the sword, it was the sword of the intellect and the convincing arguments. It is this sword that conquers the hearts and minds of men. In this context, the Quran says:
„Call on your Lord’s way with wisdom and exhortation and argue with them in the best way.“ (Quran 16: 125)
The facts speak for themselves
Indonesia is the country with the largest number of Muslims in the world and the majority of Malaysia’s population are Muslims. But no Muslim army has ever come to Indonesia or Malaysia. It is an established historical fact that Indonesia did not adopt Islam because of a war, but because of its moral message. Despite the disappearance of the Islamic government in many regions that once ruled it, its inhabitants have remained Muslim.
In addition, they have carried the message of Islam further, invited others to it, and in doing so endured harm, hardship and distress. The same can be said for those who lived in the regions of Syria and Jordan, Egypt, Iraq, North Africa, Asia, the Balkans and Spain. This shows that the impact of Islam on the population has been that of moral conviction, in contrast to the occupation by the Western colonialists who were ultimately forced to leave the countries whose peoples were only memories of suffering, sadness , Submission and oppression.
Muslims ruled Spain (Andalusia) for about 800 years. During this time, Christians and Jews enjoyed the freedom to practice their religions, and this is a well-documented fact.
Christian and Jewish minorities have survived in the Muslim countries of the Middle East for centuries. Countries such as Egypt, Morocco, Palestine, Lebanon, Syria and Jordan all have significant Christian and Jewish populations.
Muslims have ruled India for over a thousand years and therefore they would have had the power to force every single non-Muslim in India to adopt Islam, but they did not, leaving more than 80% of the Indian population non-Muslim.
Similarly, Islam quickly spread on the east coast of Africa. And here, too, a Muslim army has never hit the ground.
An article in Reader’s Digest ‚Almanac‘, yearbook 1986, provides statistics on the growth of major religions based on their percentages in the half-century from 1934 to 1984. This article also appeared in Plain Truth magazine. Islam came first with growth of 235%, while Christianity rose by 47%. There has been no “Islamic Conquest” during this 50 year period, so Islam has spread in an extraordinary way.
Today Islam is the fastest growing religion in America and Europe. Muslims are a minority in these countries. The only sword in their possession is the sword of truth. It is this sword that makes thousands convert to Islam.
Islamic law protects the privileged status of minorities, and that is why non-Muslim places of worship flourished across the Islamic world. Islamic law allows non-Muslim minorities to set up their own courts that enforce family law affecting these minorities. The life and property of all citizens in the Islamic state are considered sacred, whether Muslim or not.
It is clear that Islam was not spread by the sword. The „Sword of Islam“ has not converted all non-Muslim minorities in Muslim countries. In India, where Muslims ruled for more than 800 years, they are still a minority. Islam is the fastest growing religion in the United States and has over six million followers.
In his book The World’s Religions, Huston Smith discusses how Prophet Muhammad guaranteed freedom of religion for Jews and Christians under Muslim rule.
The Prophet prepared a document in which he stated that Jews and Christians “should be protected from any insult and harm; they should enjoy the same right as our own people to help and good service ”and further:“ they should be able to practice their religion as freely as the Muslims. ”
Smith emphasized that Muslims view this document as the first charter of freedom of conscience in human history and as a governing model for every other Muslim state.
 In his book: Islam at the Crossroads, p.8.
 Quoted in The World’s Religions by Huston Smith, Harper Collins, 1991, p. 256