No. This is not true. However, this is a common misconception in the minds of many people. The Qur'an declares:
There is no compulsion in religion. The right direction is henceforth distinct from error (Qur'an 2:256).
This Qur'anic verse shows that God has made truth and falsehood distinct from each other and people are therefore free to choose one or the other. No one can be forced to believe in a religion since belief is something very personal. One who follows the Qur'an will not try to force another person to believe.
Even the prophet Muhammad, on whom be peace, could not force another person to become a Muslim. God revealed to him the following words:
And if your Lord willed, all who are in the earth would have believed together. Would you then compel people until they become believers? It is not for any soul to believe except by the permission of Allah (Qur'an 10:99-100).
This instruction from God makes it clear that anyone is mistaken who thinks that he or she can compel others to believe. If God wanted, He could make everyone believers, but rather has given them free choice. Even so, no one can believe upon being forced. It is the grace of God on a person that will result in belief. Is there a teaching more beautiful than this? How could any true follower of the Qur'an turn around and force his faith on others? On the contrary, the Qur'an instructs its followers on how to call people to true faith as follows:
Call unto the way of your Lord with wisdom and fair exhortation, and reason with them in the better way (Qur'an 16:125).
Where does the Qur'an tell anyone to call people at the point of a sword? It does not. God instructed his messenger, on whom be peace, as follows:
Say: This is my Way: I invite unto Allah with sure knowledge, I and whosoever follows me (Qur'an 12:108).
Here again, the call is to be made with sure knowledge, with clear evidence. Putting these instructions together, a Muslim understands that he or she must present Islam with clear evidence (i.e. sure knowledge) and use wisdom and fair exhortation to reason with people to accept the evidence for faith. Where is there any mention of sword in all of this?
The Junior Encyclopedia of Canada says:
Islam is the fastest-growing religion worldwide (The Junior Encyclopedia of Canada, Hurtig Publishers, Canada, 1990, Vol.2. p.396).
What explains this phenomenon? Who is forcing anyone today to become Muslims? Muslims are not even engaged in active preaching in any noticeable degree. People are voluntarily coming into Islam because they find that Islam makes sense.
Huston Smith discusses in his book entitled The World's Religions, on page 256, how the prophet Muhammad, on whom be peace, granted freedom of religion to the Jews and Christians under Muslim rule. The prophet had a document drawn up in which he stipulated that Jews and Christians shall be "protected from all insults and vexations; they shall have an equal right with our own people to our assistance and good offices," and furthermore, that they shall "practice their religion as freely as the Muslims" (Quoted in The World's Religions by Huston Smith, Harper Collins, 1991, p.256). Smith points out that Muslims regard that document as "the first charter of freedom of conscience in human history and the authoritative model for those of every subsequent Muslim state" (p.256).
So, was Islam spread by the sword? The following short answer comes from Ira Zepp Jr., a non-Muslim, in his book entitled A Muslim Primer:
It is unfortunate that Islam has been stereotyped as the 'religion of the sword' or that Islam was 'spread by the sword.' The historical reality is that the expansion of Islam was usually by persuasion and not by military power. In any case, Islam cannot be forced on anyone; if profession of the shahadah [i.e. the declaration of Islam] is forced on someone, it is not true Islam (A Muslim Primer by Ira Zepp, Jr., 1992, Wakefield Editions, US, p.134)