The United States is one of history’s most successful aggressor nations:
We conquered almost the entirety of continental United States through a series of small but undeniably aggressive wars against the Indians who were in possession. We also made a serious but unsuccessful effort to conquered Canada in 1812. Much of the Southwest was originally taken from the Mexicans who were in occupation by two wars, one by the Texans and then, when we annexed Texas, by us. There were still many Indian tribes who did not recognize Mexican sovereignty or our sovereignty when we replaced them. The wars with Geronimo in that area were among our most difficult aggressive wars. We of course bought Florida from Spain, but only after making it clear we would compel an exit by force if they decided not to take our money.
Let us consider first the Indians. It should be said that in many cases there were European powers who claimed parts of the future United States, and they were either were forced to “cede” those parts by war, or sold them to us, but in most cases north of Mexico the area was actually controlled by Indian tribes and the European sovereignty was more or less theoretical. Until our armies had driven out the Indians it is very hard to argue that these areas were actually in our possession.
Let me begin at the very beginning with the settlement of the English colonies. Beginning with the settlements in Virginia and those in New England, colonists had gradually build up a thin layer of essentially European civilization along the Atlantic Coast of what would eventually become the United States. This colonization had proceeded by simply seizing land, sometimes compensating the Indians already there and sometimes fighting wars with them. In general apparently no one ever really considered their rights in the matter. In these areas colonial powers issued charters to their colonists that rather assumed that they had a right to do this. Locke, for example, drew up a charter for the Carolinas in which people’s ownership of land came from their farming it. He paid no attention whatsoever to the natives already there.
But it should be said that the native tribes were not absolutely peaceful. Indeed small groups of Indians tended to raid outlying white settlements. This would continue to be true almost up to the 20th century. Indeed there was one raid in which Indians attacked a federal court in the late 1980s. In what the Europeans call the seven years war and we called the French and Indian war the two major powers in the North American continent, France and England, attempted to involve the Indian tribes in their war. There were raids from some tribes on the English colonies and English entered into treaties with some of these tribes under which they would protect our colonies in return for a guarantee of their keeping’s existing tribal lands. It was this guarantee that prevented or impeded the westward push on the colonists and they objected to it.
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It should be said that the Indians in general lived by hunting and gathering and required a great deal of land to support individual families and tribes. Efforts were made, particularly in the Louisiana Purchase to get them to farm the land but this was in general unsuccessful. Thus land that might support 20,000 settlers was occupied by perhaps only 500 Indians. Purchase of the land was difficult because the Indians had no clear-cut tribal or family ownership. The individual tribes were in almost continuous minor wars with each other and hence purchase of land from one would not extinguish the claim of another. Nevertheless, with rare exceptions, we and the other “European” claimants simply ignored Indian rights and issued charters to settlers or in Mexico, conquistadors.
It is interesting that with the occupation of the entire United States by Americans we stopped engaging in wars of conquest.