Well, since we just moved to the plains as an alliance, that is the newest one. And the horde definitly shows up there

It always attacks ours in the plains, it is the one built most recently.

Which ever out of two you built first will get the horde wave .

My small alliance has two and Horde always goes for the plains HQ :)

If you have an alliance HQ in the plains and one in the wasteland, which one gets attacked during waves 10 and 20? Do they both get attacked, or just one of them?

Edit: it turned out to be the newer HQ on the plains

Which HQ does infected horde wave 10/20 attack if you have two HQs?