The power to hold is measured by the power to use; hence the weak tenure of hunting and pastoral tribes.
Between their scattered encampments at any given time are wide interstices, inviting occupation by any settlers who know how to make better use of the soil.

This explains the easy intrusion of the English colonists into the sparsely tenanted territory of the Indians, of the agricultural Chinese into the pasture lands of the Mongols beyond the Great Wall, of the American pioneers into the hunting grounds of the Hudson Bay Company in the disputed Oregon country.[106] The frail bonds which unite these lower societies to their soil are easily ruptured and the people themselves dislodged, while their land is appropriated by the intruder.

But who could ever conceive of dislodging the Chinese or the close-packed millions of India?
A modern state with a given population on a wide area is more vulnerable than another of like population more closely distributed; but the former has the advantage of a reserve territory for future growth.[107] This was the case of Kursachsen and Brandenburg in the sixteenth century, and of the United States throughout its history.

But beside the danger of inherent weakness before attack, a condition of relative underpopulation always threatens a retardation of development.

Easy-going man needs the prod of a pressing population.