Answer:
It is a common complaint among some non-Muslims
that Islam would not have millions of adherents all
over the world, if it had not been spread by the use of
force. The following points will make it clear, that far
from being spread by the sword, it was the inherent
force of truth, reason and logic that was responsible
for the rapid spread of Islam.

1. Islam means peace:
Islam comes from the root word ‘salaam’, which
means peace. It also means submitting one’s will to
Allah (swt). Thus Islam is a religion of peace, which
is acquired by submitting one’s will to the will of the
Supreme Creator, Allah (swt).
2. Sometimes force has to be used to
maintain peace:
Each and every human being in this world is not in
favor of maintaining peace and harmony. There
are many, who would disrupt it for their own vested
interests. Sometimes force has to be used to maintain
peace. It is precisely for this reason that we have the
police who use force against criminals and anti-social
elements to maintain peace in the country. Islam
promotes peace. At the same time, Islam exhorts
its followers to fight where there is oppression.
The fight against oppression may, at times, require
the use of force. In Islam force can only be used to
promote peace and justice.
3. Opinion of historian De Lacy O’Leary:
The best reply to the misconception that Islam was
spread by the sword is given by the noted historian
De Lacy O’Leary in the book “Islam at the cross
road” (Page 8):
“History makes it clear however, that the legend
of fanatical Muslims sweeping through the world
and forcing Islam at the point of the sword upon
conquered races is one of the most fantastically
absurd myths that historians have ever repeated.”
4. Muslims ruled Spain for 800 years:
Muslims ruled Spain for about 800 years. The
Muslims in Spain never used the sword to force the
people to convert. Later the Christian Crusaders
came to Spain and wiped out the Muslims. There was
not a single Muslim in Spain who could openly give
the adhaan, that is the call for prayers.
5. 14 million Arabs are Coptic Christians:
Muslims were the lords of Arabia for 1400 years.
For a few years the British ruled, and for a few
years the French ruled. Overall, the Muslims ruled
Arabia for 1400 years. Yet today, there are 14 million
Arabs who are Coptic Christians i.e. Christians since
generations. If the Muslims had used the sword there
would not have been a single Arab who would have
remained a Christian.
6. More than 80% non-Muslims in India:
The Muslims ruled India for about a thousand years.
If they wanted, they had the power of converting
each and every non-Muslim of India to Islam. Today
more than 80% of the population of India are non-Muslims. All these non-Muslim Indians are bearing
witness today that Islam was not spread by the
sword.
7. Indonesia and Malaysia:
Indonesia is a country that has the maximum
number of Muslims in the world. The majority of
people in Malaysia are Muslims. May one ask, “which
Muslim army went to Indonesia and Malaysia?”
13. East Coast of Africa:
Similarly, Islam has spread rapidly on the East Coast
of Africa. One may again ask, if Islam was spread by
the sword, “which Muslim army went to the East
Coast of Africa?”
9. Thomas Carlyle:
The famous historian, Thomas Carlyle, in his
book “Heroes and Hero worship”, refers to this
misconception about the spread of Islam:
“The sword indeed, but where will you get your
sword! Every new opinion, at its starting is, precisely
in a minority of one. In one man’s head alone, there
it dwells as yet. One man alone of the whole world
believes it, there is one man against all men. That he
takes a sword, and try to propagate with that, will do
little for him. You must first get your sword! On the
whole, a thing will propagate itself as it can.”
10. No compulsion in religion:
With which sword was Islam spread? Even if
Muslims had it they could not use it to spread Islam
because the Qur’an says in the following verse:
“Let there be no compulsion in religion: Truth
stands out clear from error”
[Al Qur’an 2:256]
11. Sword of the Intellect:
It is the sword of intellect. The sword that conquers
the hearts and minds of people. The Qur’an says in
Surah An Nahl, Chapter 16 Verse 125:
“Invite (all) to the way of thy Lord with wisdom
and beautiful preaching; and argue with them in
ways that are best and most gracious.”
[Al Qur’an 16:125]
12. Increase in the world religions from:
1934 to 1984
An article in Reader’s Digest ‘Almanac’, year book
1986, gave the statistics of the increase of percentage
of the major religions of the world in half a century
from 1934 to 1984. This article also appeared in ‘The
Plain Truth’ magazine. At the top was Islam, which
increased by 235%, and Christianity had increased
only by 47%. May one ask, which war took place in
this century which converted millions of people to
Islam?
13. Islam is the fastest growing religion in:
America and Europe
Today the fastest growing religion in America is
Islam. The fastest growing religion in Europe is
Islam. Which sword is forcing people in the West to
accept Islam in such large numbers?
14. Dr Joseph Adam Pearson:
Dr Joseph Adam Pearson rightly says, “People
who worry that nuclear weaponry will one day fall
in the hands of the Arabs, fail to realize that the
Islamic bomb has been dropped already, it fell the
day MUHAMMAD (pbuh) was born.”