Classic method is to cut it within a few inches of the ground. And then, after it sends up a bunch of shoots, cut those back. That way you get a dense hedge from the bottom up. Left to its own devices it will be bare at the bottom and bushed out at the top which is not what you want.

Thanks, that's what I'll do!

Mine were stripped of half their bark before I caught it and enclosed them
in chicken wire. Rabbits, apparently.

They have one trunk each, about an inch in diameter, no shoots or suckers
from ground level.

The branches are chewed back to about 18", but it's the stripped bark that
worries me most.
Any advice?

Cut back in spring to just about ground level - they'll come back.