The doctrine or “right” of conquest goes back to Roman times and, apart from the criticism aimed at Spain in the 1500s, remained mostly uncontested until the late eighteenth century, when — with the breaking free of the Americas from Europe — the doctrine found new champions and new critics.
The leaders of the new United States reinforced the doctrine, invoking the right of conquest to justify their drive westward toward the Pacific Ocean and their taking of Native American and Mexican lands.
Generations of law professors in the U.S. taught their students that the doctrine was legitimate. “The title of European nations, and which passed to the United States, to this vast territorial empire, was founded on discovery and conquest,” as James Kent put it at Columbia Law School in the 1790s. The Supreme Court, too, said that the United States was founded on conquest, and that its doctrine remained applicable. As late as 1928, a widely-assigned English-language law book insisted that, “as long as a Law of Nations has been in existence, the States, as well as the vast majority of writers, have recognized subjugation as a mode of acquiring territory,” deeming it legal for “the victor to annex the conquered enemy territory.”
In contrast, Spanish America’s independence leaders fiercely repudiated the principle of conquest. They had to, since they had to learn to live with each other, for they presided over seven new Spanish-American republics on a crowded continent. If they had adhered to a U.S. version of international law, what would have stopped Argentina from conquering Chile the way the United States conquered the Creeks and the Mexicans? Or Chile from marching on Argentina to gain access to the Atlantic? The result would have been endless war. And so, the region’s jurists and other intellectuals (drawing from earlier Catholic criticisms of Spain’s subjugation of the New World) disavowed conquest. In its place, they cobbled together a new framework of international relations that outlawed aggressive war and recognized the absolute sovereignty of all nations, regardless of their size.
For decades, Latin American diplomats tried to force Washington to accept such a vision of cooperative international law — and for decades Washington refused, not wanting to be a Gulliver tied down by a gaggle of Latin Lilliputians. Over time, however, U.S. statesmen began to grudgingly accept Latin America’s legal interpretations, with the far-sighted among them realizing that a reformed system of international law would allow for a more effective projection of Washington’s power. In 1890, at the first Pan-American Conference, the United States signed a provisional treaty abrogating the doctrine of conquest. In 1933, President Franklin Delano Roosevelt agreed to give up the right to intervene in Latin American affairs and to recognize the absolute sovereignty of all nations.
