{ It is not for a prophet to take captives until he has wreaked havoc on the land; you desire the fleeting gain of this world but Allah desires the hereafter; and Allah is mighty, wise } Al-anfal 67

“Wreaking havoc” is plentiful killing, and spreading it heavily in harshness and intensity; the intent is to degrade disbelief and weaken it, and to strengthen Islam and make it manifest, by spreading killing among the Disbelievers.