Allah (Exalted be He) has made Jihad lawful for the purpose of spreading Islam and overcoming obstacles which Du`ah (callers to Islam) are faced with while calling others to the truth and preventing those whose souls may prompt them into harming or assaulting the Du`ah. Thus Jihad serves as a means that safeguards against the occurrence of Fitnah (sedition), provides an atmosphere of peace and security, ensures supremacy of Allah's Word and lowness of the Kafir's (disbelievers) word, and guarantees that people enter Islam in multitudes. Allah (Exalted be He) says:
And fight them until there is no more Fitnah (disbelief and polytheism, i.e. worshipping others besides Allâh) and the religion (worship) will all be for Allâh Alone [in the whole of the world]. But if they cease (worshipping others besides Allâh), then certainly, Allâh is All-Seer of what they do.
Allah also says:
...and fight against the Mushrikûn (polytheists, pagans, idolaters, disbelievers in the Oneness of Allâh) collectively as they fight against you collectively. But know that Allâh is with those who are Al-Muttaqûn (the pious).
In another place Allah says:
It is He Who has sent His Messenger (Muhammad صلى الله عليه وسلم) with guidance and the religion of truth (Islâm), to make it superior over all religions even though the Mushrikûn (polytheists, pagans, idolaters, disbelievers in the Oneness of Allâh) hate (it).
Thus, it should be known that Jihad has been made lawful to take people out of the darkness of Kufr (disbelief) into the light of Iman (faith). Another purpose for which Jihad has been made lawful is to defend (Part No. 12; Page No. 14) Muslim territories against aggression of its enemies.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.