DEFENSIVE WAR
To those against whom war is made, permission is given (to fight), because they are wronged, and verily, God is most powerful for their aid. They are those who have been expelled from their homes in defiance of their rights - (for no cause) except that they say, "Our Lord is God." (Al Quran 22:39 and 40)
'Fight in the cause of God those who fight you, but do not transgress limits for God loveth not transgressors'. (Al Quran 2:190)
WAR, CEASEFIRE AND PEACE
And fight them on until there is no more oppression, and there prevail justice and faith in God, but if they cease let there be no hostility except to those who practise oppression. (Al Quran 2:193)
But if the enemy incline towards peace, do thou (also) incline towards peace, and trust in God: for He is One that heareth and knoweth (all things) (Al Quran 8:61)