What base should defense units be stationed at? (Little Upsilon)

When I create a defense unit on LU it tells me to select an offensive base to station the unit at,it seems like it would be a defensive base? Or does that not matter. I tried air,land and supply it said offensive base for all of them.

It has to be at an offensive base. I suppose defenseive bases are just where theyre stored.

A question though. If your country is attacked, and you have land based divisions, do they automatically defend your country by moving to attack the land attackers? or are they manually moved?

And if they do have to be manually moved how is it done. I can't find the button anywhere

Thanks

One way is by going to the tab War > Military Units > Show Land Forces. Then a list of your land units pops up and if you clk the coordinates it says the unit is at, a big map appears allowing you to move them.