You, as Muslims, cannot help but fight those who attacked and fought you, unless they resort to a people between you and them there is a covenant. Look at respecting covenants and treaties, for a terrorist has no covenant or treaty, but in the Islamic religion, even the aggressor, if he resorts to a people between you and them a covenant, stop fighting him.

(… أَوْ جَاءُوكُمْ حَصِرَتْ صُدُورُهُمْ أَن يُقَاتِلُوكُمْ أَوْ يُقَاتِلُوا قَوْمَهُمْ …) (…or those who come to you, their hearts strained at [the prospect of] fighting you or fighting their own people.…): Meaning, they do not want to fight you neither fight their people.

( فَإِنِ اعْتَزَلُوكُمْ فَلَمْ يُقَاتِلُوكُمْ وَأَلْقَوْا إِلَيْكُمُ السَّلَمَ فَمَا جَعَلَ اللَّهُ لَكُمْ عَلَيْهِمْ سَبِيلًا … ) (…So if they remove themselves from you and do not fight you and offer you peace, then Allah has not made for you a cause [for fighting] against them.): Then Allah (swt) does not accept that you have a way against them, neither to kill them, nor to harm them, nor any kind of aggression towards them. These are the laws of war and the battlefield, and they are just and peaceful laws as well, for they exclude those who resort to those with whom you have covenants and also those who say the word of peace.