It took a definitive shape in the reign of King James I of England when all the counties of Ireland were eventually sh he maximum area within which Ulster Protestants/unionists could be expected to have a safe majority.
It took a definitive shape in the reign of King James I of England when all the counties of Ireland were eventually shired. The area of Northern Ireland was seen as the maximum area within which Ulster Protestants/unionists could be expected to have a safe majority.