Had Muslims adopted a strategy of propagation of Islam by the sword then they would have gone against the following fundamental tenet of the Holy Quran:
There should be no compulsion in religion. Surely, right has become distinct from wrong… (Ch.2: V.257)
They would also have gone against the example of the founder of Islam, The Holy Prophet(sa), who always opted for the most peaceful and just strategy in any situation. His example of peace and forgiveness is matchless.
A prime example of his life of peace is when the Muslims, headed by the Holy Prophet(sa), entered Makkah with a ten thousand strong army. At that historic occasion when they were in a position of strength they did not impose Islam on a single person nor punish anyone for not becoming a Muslim, despite the fact that it would have been very easy for them to have done so. Instead the Holy Prophet(sa) left all to practise their religion freely and through this he underlined the true message of Islam.
It is true the Qur’an instructs that each Muslim must take it upon him or herself to propagate the message of Islam in the best of ways and by reason and persuasion, but there is absolutely no room for force of any kind:
Call unto the way of thy Lord with wisdom and goodly exhortation and argue with them in a way that is best. Surely, thy Lord knows best who has strayed from His way; and He also knows those who are rightly guided. (Ch.16: V.126)
Furthermore, for the Holy Prophet(sa) himself the Qur’an clearly stated that his mission was to convey the message of Islam but thereafter it was down to the people to accept or reject this message and this choice was without any coercion of punishment since they were accountable for this decision to God and not to man.
The Qur’an states,
But if they turn away We have not sent thee as a guardian over them. Thy duty is only to convey the Message…. (Ch.42: V.49)
This makes clear that the only duty for Muslims with regards to the spread of Islam is to convey its message and any action that even hints of coercion or force has no basis in Islam.
In this respect it is interesting to note that the largest Muslim population in the world is to be found in Indonesia, which accepted Islam through early dialogue with Muslim traders and holy men. The second largest Muslim population belongs to India which is not even a Muslim country having a Hindu majority. More recently we know that in Europe Islam is the fastest growing religion, yet no sword is used to persuade such people of the beauties of Islam. This emphasis on learning and knowledge as a path to success is captured in the famous saying of the Holy Prophet(sa):
‘The ink of the scholar is more precious than the blood of the martyr.’ (Bukhari, Book of Knowledge)