Not wholly, but in great measure, to strike the greater terror into the inhabitants, and to make their conquest of the place more easy.
Related Commentaries of Judges 18:27
Judges 18:27
27 And they took the things which Micah had made, and the priest which he had, and came unto Laish, unto a people that were at quiet and secure: and they smote them with the edge of the sword, and burnt the city with fire.