If you invade a planet with enemy PDS but no Ground Forces present, do the PDS fire?

Thanks

Wak

Yes, the PDS will fire. However, unless you have more (or equal) PDS than they have invading GFs, all your PDS will be able to do is whittle down the invaders a little bit (which may make it easier to take).

Essentially, the PDS systems are automated and/or controlled by their own crew, they are not fired by the troops themselves