God says in the Holy Qur'an in Surah Baqara (190-191):

"And fight in the way of God, those who fight you and do not transgress, for God does not love transgressors. And kill them whenever you find them, and expulse them wherever they expulsed you; and oppression is worse than carnage; and do not fight them at the Sacred Mosque unless they fight you there, and if they fight you, then kill them. Indeed such is the recompense of disbelievers, and if they regress back then God is forgiving and compassionate."

This verse -from Chapter Al Baqara- has always been widely misused by the anti-Islam propagandists so as to prove their silly propaganda that the Qur'an teaches the killing of infidels. Today, I was reading a book about the reasons of the revelation of the Holy Qur'an, and I came accross this verse that triggered so much thoughts among some people lacking the proper understanding of Qur'an, while for some it just paved them the way to justify a subconscious xenophobia. This verse refers to one of the most delicate times in the history of Islam, when the Meccan persecutions against Muslims and the Prophet Muhammad (pbuh) went too far as to prevent them from performing their rituals of pilgrimmage, and which leaded to the Treaty of Al Hudaibia, in which the Prophet Muhammad (pbuh), with the help and advice of lady Oum Selma, showed a great sense of wisdom.

The Prophet Muhammad (pbuh) marched from the Medina Monwara towards Mecca accompanied by 1400 Muslims to perform the rituals of pilgrimmage. During their peacefull caravan, Muslims received the information that the 'Meccan disbelievers' were plotting against them as to prevent them from performing their sacred rituals by force. So, the Prophet Muhammad (pbuh) and Muslims stopped in a place called Al Hudaibia and sent them this message:

"We have come on a peaceful and religious mission. We have come only to perform the sacred pilgrimage. We desire neither bloodshed nor war, and we shall be glad if the Meccans agree to a truce for a limited period."

Whenever the Prophet Muhammad used to send a messenger among his community, this latter failed to return, till the third time when the Meccan disblievers of Quraish detained the messenger and spread a rumor that this man was killed as to provoke a war with Muslims. At this time, the Prophet collected all the Muslim people travelling with him and took pledge from them that they will fight with him if any war would be stirred against them, which the Muslims agreed upon willingly. As soon as the disbelievers knew of this pledge, they sent a messenger to negociate with the Prophet and ask peace under the following conditions:

1-Muslim should go back to Mecca without performing pilgrimmage.

2-They would be allowed till the following year under the condition that Muslim are allowed a delay of only three days to leave.

3-Muslim are forbidden to take any Muslim Meccan resident with them.

The Meccan disbelievers used these terms to provoke the Prophet Muhammad (pbuh), which he accepted by the advice of lady Oum Selma. So the Prophet acceted their terms as he wanted to avoid war and bloodshed, despite the refusal of Omar Ibn Khattab to comply. Once the term of one year was over, and the Muslims pilgrims who prepared themselves to the travel and this with 10.000 people, Muslims feared that the disbelievers breach their the Treaty of Hudaibia, as they were reluctant to fight in this month, which they considered as the sacred month. So, God revealed this verse to the Prophet and gave them permission to fight back if Meccan disblievers hindered them from their religious rituals.

This is the famous treaty of Al Hudaibia, which has been a turning point in Islamic history, and which helped the spread of Islam in the country. So, the reasons of the revelation of this verse is a clear indication that the famous 'killing of the infidels' refered to the disbelievers among the people of Mecca, named Quraish. However, the divine permission to fight was allowed unless the disbelievers breach their treaty, which is quite clear from the Qur'anic verse.