从撒丁岛的内陆到日耳曼尼亚中部和爱尔兰西部，there is a lot of land that is selectable and usually populated, yet uncolonized and seemingly empty on the political view. Currently owned territories might also be colonized if they are completely depopulated, particularly through slavery during wars. These uncolonized territories might and often do, however, have pops with their own religions and cultures. 殖民 和 定居 是一个国家可以控制这些地块的两种办法，but countries with access to the (unrecognized string “construct border fort” for Template:Icon) Construct Border Fort unit action can also use that to colonize territories.
A territory is colonized by moving one pop of any social class but slaves to it. This can be achieved by pressing the Colonize button in the territory view of the uncolonized territory and can be done at any time, as long as the following conditions are met for at least one owned territory:
- Is adjacent to or within 2 sea tiles of the target territory
- Has at least (unrecognized string “population” for Template:Icon) 10 pops.
- Has a dominant culture that is an (unrecognized string “integrated” for Template:Icon) integrated (including the primary culture)
- Has the state religion as the dominant religion
- Has at least one pop that is not a slave (note: this non-slave pop does not have to be an integrated culture or the state religion)
- Has not been used to colonize in the last year
Colonization also costs (unrecognized string “wealth” for Template:Icon) 10 gold.
When the "colonize" button is pressed, one non-slave pop (which may or may not be of an integrated culture or the state religion) moves to the colonized territory, and the territory is added to the colonizer's state.
Notably, newly colonized territories do not have any colonization cooldown and can themselves be used as a base to immediately colonize another neighbouring territory, even on the same day they were colonized. This means that, if the country has a lot of (unrecognized string “wealth” for Template:Icon) gold, large amounts of territories can be colonized in a single day by constantly moving enough slaves ) or tribesmen if the country is tribal) of an integrated culture and state religion into the newly colonized territory to bring its (unrecognized string “population” for Template:Icon) population up to 10 and give it a dominant integrated culture and state religion, making it immediately eligible to colonize another adjacent territory. This is possible mainly because most uncolonized provinces usually have at least one non-slave pop (usually a tribesman) which can be used to colonize. Moving all these pops, however, can be quite expensive is generally only viable for at least moderately-sized countries.
Migratory Tribes have the ability to turn all pops (min 3, max 20) in a territory with the primary culture (but not other (unrecognized string “integrated” for Template:Icon) integrated cultures) as dominant into migration units, for a base cost of (unrecognized string “stability” for Template:Icon) -8 stability (certain laws and your level of centralization modify this number, though the (unrecognized string “migration cost” for Template:Icon) migration cost modifier), with each pop becoming one cohort. These Light Infantry cohorts can use the (unrecognized string “settle” for Template:Icon) settle unit ability to settle in any owned or uncolonized territory, turning into tribesmen of the primary culture and religion. For uncolonzied territories, this can done as long as they outnumber the existing pops, no matter how close or far the territory is from the country's current territory (if it has any), and immediately grants ownership of the territory to the settling country. Like colonization, all pre-existing pops are kept with their culture, religion, and class.
Migration units do not require military access to cross borders, and enjoy reduced attrition. Settling also works with foreign land a tribe currently controls in a war.
Construct Border Fort
Countries with (unrecognized string “military tradition” for Template:Icon) Italic traditions (requiring the Italic culture group) can use the (unrecognized string “construct border fort” for Template:Icon) Construct Border Fort unit ability to colonize adjacent provinces once they have unlocked the ability in their tradition tree. This action can be taken by an army with a (unrecognized string “position” for Template:Icon) general and at least 5 cohorts, and for uncolonized territories requires that the territory is adjacent to a currently owned territory and does not have neighbour any owned territories that already have a (unrecognized string “fortress” for Template:Icon) fortress building. Constructing the border fort costs 3000 manpower and will give ownership of the border territory as well as automatically constructing a (unrecognized string “fortress” for Template:Icon) fortress and creating a freeman pop of the primary culture and religion there. The army that built the fort can be used to construct new border forts as soon as it moves to a new neighbouring uncolonized territory as long as the country has enough manpower, though if adjacent territories want to be colonized the just-built (unrecognized string “fortress” for Template:Icon) fortress will need to be scrapped first.