If your ground is infested with 'ground elder' it will find its way back whatever you do. It must be the most tenacious plant ever, because it will re-grow from the tiniest fraction of leafless root left behind, and seemingly no matter how deep it is in the ground.
In our old house, before I knew what it was, I let it spread because the leaf, (it doesn't flower), is quite attractive, and we became overrun and never conquered it. In my present much smaller garden, I've spent two years dealing with an outbreak introduced by a plant donated by a friend, and it's still showing up after a short period of rest after I've attacked it.
In a raised bed, we have put down bark chippings which suppresses many weeds, and this makes the appearance of this curse easy to spot as it pushes up from below. I then dig down, sometimes to 18 inches or more, tracing the root, which has often spread underground and try to remove it intact. Just when I think we've cracked it, up it comes again. Definitely getting paranoid about it, and although I'm slowly getting there, this is in a small confined area.
The trouble with using large quantities of aggressive blanket weedkiller is the drastic effect they have through getting into water courses etc., and it has to be used very carefully. Remember also that Sodium Chlorate is very toxic, kills everything, and can cause spontaneous combustion on fabrics if stored in the right (or wrong), conditions. If you want to keep a garden weed free, it means continual hours of attention with little let up in the attack.
Good luck, Tunnie.