No Compulsion

Islam believes in the right of every person to be able to choose their religion based on their own understanding & free will. Quran professes that a person shouldn't be forced in choosing a religion since forceful conversion is not what is divinely required.

So if they dispute with thee, say: "I have submitted My whole self to Allah and so have those who follow me." And say to the People of the Book and to those who are unlearned: "Do ye (also) submit yourselves?" If they do, they are in right guidance, but if they turn back, Thy duty is to convey the Message; and in Allah's sight are (all) His servants. (Chapter 3 Al-E-Imran:20)

If Allah wanted, no one in the entire universe would have had the courage to go against His desire but the test of this world was designed with a set of pre-defined rule to judge every individual by giving them the apparatus of free will for their actions. Based on that principal, prophet Muhammad(peace be upon him) propagated the religion of Islam to the followers of all faiths but no one was forced or compelled to change their religion.

Let there be no compulsion in religion: (Chapter 2 Al-Baqra:256)

Muslims are instructed to make efforts towards establishing the kingdom of heaven on this earth just like Jews and Christians before them were instructed. That effort, however, should primarily be made in a Muslim dominated society. There is no forceful conversion allowed in Islam and the history of Muslim Spain and former Indian subcontinent tells the entire story where muslims, who ruled for centuries, are still is minority. Islam is the religion of peace standing against all aggression on this earth and is ready to offer its assistance to all humanity regardless of the faith, color, cast & nation of the suppressed.