Militia not engaging passing army

Giving me error trying to upload png image. I did down size below 2 MB. Anyway a level 1 militia passed right through my level 2s and took the province. Now I'm in pursuit.

Now I blew past him. Seems they will only engage if my militia was sitting on control point. There was no way to defend, I had to attack to engage.

Just added the pictures. So is this how it always is? If I'm on the control point I would defend, but if I'm stopped away from the control point, he will pass right through me. So I can't leave anti tanks away from dot if I want them to defend in forest?