For a while the middle easterners were taking any Roman Citizen they could find and beheading him.
The Romans sent their legions to the middle east. When a Roman was killed they rounded up 1,000 Arabs nearest to where the Roman was killed and beheaded them all.
One Roman = 1000 Arabs. With in a few weeks any Roman citizen could walk unarmed at midnight on a dark night anywhere in the middle east in complete safety. The local citizens would kill any terrorist who even talked about or looked like he might be there to attack a Roman.
It is the same sort of technique still in use in the American Army in the late 1950s. If one member of your platoon screwed up, You punished the entire platoon. Soon you had 43 members of the platoon seeing to it the 44th member did not screw up.
Ah ... memories.
I hate to say it but it would seem that the last person (on our side) with any b@lls was Harry Truman when he ordered the Atomic Bombing of Japan.
After the 2nd one - the Japanese in power got the message.