at this precarious juncture with quraish, intent on pursuing their aggressive and devilish plans, allâh, the all-high, gave the muslims the permission to take arms against the disbelievers:

"permission to fight is given to those (i.e. believers against those disbelievers), who are fighting them, (and) because they (believers) have been wronged, and surely allâh is able to give them (believers) victory." [al-qur'an 22:39]

this verse was revealed in a larger context of divine instructions to eradicate all aspects of falsehood, and hold in honour the symbols and rites of allâh:

"those (muslim rulers) who, if we give them power in the land, (they) order for iqamat-as-salât: [i.e. to perform salât (prayer) — the five compulsory, congregational prayers (the males in mosques)], to pay the zakat (obligatory charity), and they enjoin al-ma‘ruf (i.e. islamic monotheism and all that islam orders one to do), and forbid al-munkar (i.e. disbelief, polytheism and all that islam has forbidden) [i.e. they make the qur’ân as the law of their country in all the spheres of life]." [al-qur'an 22:41].

doubtlessly, the permission to fight was revealed in madinah after emigration, not in makkah, still the exact date where of is in doubt.

the permission to fight was already there, but in the light of the status quo, it was wise for the muslims to bring the commercial routes leading to makkah under their control. to realize this strategic objective, the prophet [pbuh] had to choose either of two options:

1. entering into non-aggression pacts with the tribes inhabiting either the areas adjacent to the routes or between these routes and madinah. with respect to this course of action, the prophet [pbuh] had already signed, together with the jews and other neighbouring tribes, the aforementioned pact of cooperation and good neighbourliness.
   
2. despatching successive armed missions for harassment along the strategic commercial routs.