More fighting (why the fighting?) also Establish regular prayers
"But when the forbidden months are past, then fight and slay the Pagans wherever you find them, and seize them, beleaguer them, and lie in wait for them in every strategem (of war); but if they repent, and establish regular prayers and practice regular charity, then open the way for them: for Allah is Oft-forgiving, Most Merciful." [Qur'an 9:5]
Use all means to kill them and establish an Islamic way of life in the survivors.
"How can there be a league, before Allah and His Messenger, with Pagans, except those with whom you made a treaty near the Sacred Mosque? As long as these stand true to you, you stand true to them: for Allah loves the righteous. How (can there be such a league), seeing that if they get an advantage over you, they do not respect in you the ties either of kinship or of covenant? With (fair words from) their mouths thet entice you, but their hearts are averse from you; and most of them are rebellious and wicked." [Qur'an 9:7-8]
"Fight those who do not believe in Allah nor in the Last Day, nor hold that forbidden which has been forbidden by Allah and His Messenger, nor acknowledge the Religion of Truth, (even if they are) of the People of the Book, until they pay the Jizya with willing submission, and feel themselves subdued." [Qur'an 9:29]
This completely invalidates the UBL offer of a truce with Europe since he did not demand they adopt the true faith or at least pay the charity required by Islam and "feel subdued" and the Europeans (by and large) do not share a "kinship" with the terrorists.
I hope that anyone considering his "offer" reads this and thinks carefully.