"Take no prisoners"-what does this phrase mean?

That is a term used I war it means to kill everyone ( take no prisoners or people alive) so yea kill everyone

Back in the day a prisoner was set aside until usually it was decided what to do with them. A lot of times they were breezed over and forgotten about. So the phrase may mean cut to the case and get the work done now not later, if that does fit the context correctly

It's kind of like jumping out of a plane without a parachute. (As a pilot, I definitely don't recommend this.) Without Jesus, all you are is a pile of goo on the ground. In fact, rescue personnel would probably be really lucky to find goo. Most times all they find is a pair of pants, a shirt, and shoes. The body hits with THAT MUCH impact. If you turn to Jesus, your chances of survival after pulling a D.B. Cooper are infinitely greater. God Bless you- Captain Art Griego

Ask him. Say "I thought I knew what it meant but when you use it I'm not always sure I have understood what you meant". It's his job to communicate clearly. Maybe he should drop phrases like that which aren't clear in the context he uses them.

Seeing as your instructor probably isnt teaching you to kill everyone, Im pretty sure he just means "Go all out".. Or "try your best" if that one confused you.

To take no prisoners is to kill everyone in war

I take it to mean the same thing as to leave no stone unturned (try every possible course of action in order to achieve something.)

The statement just means do not show any mercy.

take no one alive in war

Don't leave any witnesses, kill everyone.