Belligerent destroying mortars and guns here and there (6-3)
I believe the answer is:
strong-arm
'belligerent' is the definition.
(I've seen this before)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for strong-arm that I've seen before include "These tactics use force or strength - ask Armstrong" , "(Of tactics) using violence" , "Using force/violence" , "Using force or violence" , "These tactics use force, like Armstrong" .)