What is permission for battle? What does fight those who fight you means? Who is the enemy of Muslims?
The Noble Messenger -upon him blessings and peace- had not been given permission at first to take up arms against the idolaters, responsible only with inviting them to believe in the unity of Allah, glory unto Him, and in turn endure and turn a blind eye to the possible retaliations of their ignorant, in the form of torture and malignant behavior. Heartened, the idolaters of Quraysh were not letting the least opportunity go to exact torment on the followers of the Blessed Prophet -upon him blessings and peace-, in hope of turning them back to their pagan beliefs of old. And through persistently meting out the most ruthless forms of torture, they did succeed with some, while others were forced to leave their hometown for Abyssinia and then Medina, just for the sake of preserving their faith.
Events were taking such sharp turns for the worst that it had become almost impossible to maintain peace through the policy of ‘endurance and patience’, observed by the Blessed Prophet -upon him blessings and peace- until then. Even the adoption of self-defense could not even stem the tides of agony, forcing the Blessed Prophet -upon him blessings and peace- to seek refuge in the Almighty, and anticipate a relieving Revelation.
Ultimately, as the idolaters were at an all-time low in their adamancy of denying all the blessings bestowed on them by the Almighty and of rejecting of the Noble Messenger -upon him blessings and peace- ; and at a time, when they were a cause of anxiety for Muslims even after their immigration, the ayat giving Muslims permission to fight back were revealed, stressing the need of self-defense which had by now become a matter of immediate urgency:
“Permission (to fight) is given to those upon whom war is made because they are oppressed, and most surely Allah is well able to assist them. Those who have been expelled from their homes without a just cause except that they say: Our Lord is Allah. And had there not been Allah’s repelling some people by others, certainly there would have been pulled down cloisters and churches and synagogues and mosques in which Allah’s name is much remembered; and surely Allah will help him who helps His cause; most surely Allah is Strong, Mighty.” (al-Hajj, 39-40)
“And fight in the way of Allah with those who fight with you, and do not exceed the limits, surely Allah does not love those who exceed the limits.” (al-Baqara, 190)
And as for the legitimate reasons and purposes for fighting, the Almighty proclaims:
“And fight with them until there is no more persecution and religion should be only for Allah…” (al-Anfal, 39)
The permission to fight is a result of the hostile attitude adopted against Islam and Muslims. Jihad has thus been decreed obligatory in order to safeguard and defend, against assaults, the daruuraat’ul-khamsa, or five imperatives, values which are vital for the survival of the existence of society. These are the protection of property, human life and progeny, reason and religion. The Divine Command carries the purpose of punishing those liable for the crime of swaying others away from the Truth and getting rid of all hindrances that stand in the way of its communication.
That Muhammad Mustafa, the pinnacle of all prophets -upon him blessings and peace-, sent as a mercy to entire humankind, had to engage in great and demanding battles despite nurturing an unfathomable compassion enough to take entire humankind under its shade, was necessitated by the need of establishing social peace and stability and consolidating the struggle for tawhid. The hadith, “I am a prophet of mercy and warfare”, (Ahmad, IV, 396) should therefore be understood along these lines.
Accompanying the ayah that gave permission to fight back were others encouraging the Prophet -upon him blessings and peace- and the Believers to act in accordance with the Divine sanction:
“O Prophet! Allah is sufficient for you and for such of the believers who follow you. O Prophet! Urge the believers to war.” (al-Anfal, 64-65)
“What! Will you not fight those who broke their oaths and aimed at the expulsion of the Messenger, and they attacked you first; do you fear them? But Allah is most deserving that you should fear Him, if you are believers. Fight them, Allah will punish them by your hands and bring them to disgrace, and assist you against them and heal the hearts of a believing people. And remove the rage of their hearts; and Allah turns (mercifully) to whom He pleases, and Allah is Knowing, Wise.” (at-Tawba, 13-15)
In addition, there came Revelations warning against falling behind from jihad:
“Warfare is ordained for you, though it is hateful unto you; but it may happen that you hate a thing which is good for you, and it may happen that you love a thing which is bad for you. Allah knows; you know not.” (al-Baqara, 216)
“It is not for the townsfolk of Al-Madinah and for those around them of the wandering Arabs so stay behind the messenger of Allah and prefer their lives to his life.” (at-Tawba, 120)
“Say: If your fathers, and your sons, and your brethren, and your wives, and your tribe, and the wealth you have acquired, and merchandise for which you fear that there will no sale, and dwellings you desire are dearer to you than Allah and His messenger and striving in His way: then wait till Allah brings His command to pass. Allah guides not the wrongdoing folk.” (at-Tawba, 24)
Compliant with these Divine commands, following the lead of the Blessed Prophet -upon him blessings and peace-, the Believers began a serious preparation to combat the idolaters.