[Peacekeeper]

Every nation has certain units it can only recruit in its capital city(the one you start with and on most maps named after your nation). Only that nation can recruit those units out of that province.

The up side to conquering these(other than eliminating your enemy) is that the population is usually very high(all but Ermor death themes start with 29k+ population) and the province will have a high gem income already in place. You should note that Capitals never have hidden gem sites, so there is no point in site searching them.

Hope this helps.