How do you micro militia/man at arms when trying to kill vils?

Killing vils with scouts is pretty easy,even with archers I'm slowly learning.

But it seems so hard with infantry,whether it be in a drush or m@a flush.The kill is only guaranteed when you trap a vil against the wood line.Otherwise they just run back.Infantry never catches up and I end up taking tc damage.

So is there anything with the placement before attacking,the movement during attacking that I need to do to guarantee kills?