Assuming that this was an unknown, unforeseen attack on Israel, the inference is that their intelligence apparatus in Gaza was beyond terrible.
With that inference assumed, the ability to kill off terrorists associated with Hamas within Gaza seems very difficult to do now or in the future. I'm hearing reports that most of the officer apparatus of Hamas lives an opulent life in Doha and elsewhere while street thugs are recruited on the ground.
@Red Leg I'm not sure how you cut the head off the snake, much less kill the snake in the above scenario?
Killing those with guns is one obvious option, but what happens when they drop their rifles and blend into the populace? How does Israel do any of this without an occupancy force for years, interviewing neighbors, etc? They'd have to occupy Gaza and overthrow the government to clean house?