We are dense. Last tweaks sent a lot of the monsters that used to focus on Westgard off to the rest of the continent, where many realms have still not recovered. We got bigger, but not as much as everyone else got smaller, continental density is thus still lower than what it was at when the last invasion was triggered.
That, and, well... we did kill like 100 000 CS of rogues this month. At least 60k in the last few weeks, in any case. And it ain't the first time we grow this big, I think we had 4 more regions than we have now when the last invasion was triggered (current extent + Mountain of Woe, Gaston Farms, Gaston, and Jorradith). I haven't been in any rush to reclaim those precisely to keep density high enough, hence why we went to kill the hordes in Eidulb Outskirts and Duil (5k + 18k, better to kill them there before they reach us).
I don't really understand how come the other realms have failed to recover, but Westgard has an active and efficient military. We *never* sit around for nothing.
