"And did not Allah check one set of people by means of another,
the earth would indeed be full of mischief;
but Allah is full of Bounty to all the worlds"
Islam never tolerates unprovoked aggression from its own side; Muslims are commanded in the Qur'an not to begin hostilities, embark on any act of aggression, violate the rights of others, or harm the innocent. Even hurting or destroying animals or trees is forbidden. War is waged only to defend the religious community against oppression and persecution, because the Qur'an says that "persecution is worse than slaughter" and "let there be no hostility except to those who practice oppression" (Qur'an 2:190-193). Therefore, if non-Muslims are peaceful or indifferent to Islam, there is no justified reason to declare war on them.
The Qur'an describes those people who are permitted to fight:
"They are those who have been expelled from their homes
in defiance of right, for no cause except that they say,
'Our Lord is Allah.'
Did not Allah check one set of people by means of another,
there would surely have been pulled down monasteries, churches,
synagogues, and mosques, in which the name of God is commemorated
in abundant measure..."
Note that the verse specifically commands the protection of all houses of worship. Finally, the Qur'an also says, "Let there be no compulsion in religion" (2:256). Forcing someone at the point of a sword to choose death or Islam is an idea that is foreign to Islam in spirit and in historical practice. There is absolutely no question of waging a "holy war" to "spread the faith" and compel people to embrace Islam; that would be an unholy war and the people's forced conversions would not be sincere.