As early as the 1820s, the U.S. Government set the stage for continental, if not hemispheric, expansion when President James Monroe expressed his doctrine to Congress. The Monroe Doctrine (MD) warned off former and future European colonizers from any new exploits in the western hemisphere. The MD was backed up with the threat of war by the upstart new military power on the global block, "...;We owe it...; to declare that we should consider any attempt on their part to extend their system to any portion of this hemisphere as dangerous to our peace and safety."(Dorf, p.772) The MD in effect isolated Mexico and Native Americans from the potential of European intervention on their behalf. Hence, westward expansion could proceed unencumbered dooming Mexican and Native American territory to a fate to be determined solely by the government of the U.S. The same government had shown its disdain for Native Americans with the Indian Removal Act of 1830 and Andrew Jackson's nullification of the Supreme Court's decision overturning the deceptive Treaty of New Echota, which gave away Cherokee land on the signature of hand picked, but unauthorized Cherokees.
It should be kept in mind that the flowery language of the Declaration of Independence, "...;that all men are created equal, that they are endowed by their Creator with certain unalienable rights, that among these are life, liberty, and the pursuit of happiness...;"(Dorf, p.157 ) in the words of Thomas Jefferson, and the promise held by the language in the Preamble of the U.S. Constitution, "...;establish justice...; promote the general welfare, and secure the blessings of liberty to ourselves and our posterity...;" (Dorf, p. 214 ) as probably composed by James Madison, were empty of meaning for Mexico and the tribes of North America. Both Native Americans and the people of Mexico were descendants of indigenous peoples who had witnessed the arrival of the first Europeans. The Native Americans who inhabited the Atlantic coastal region when Europeans arrived had yet to reach mutually acceptable living arrangements with their uninvited guest in the early 19
Century after four centuries of uneasy coexistence. The Native Americans of the east, while undoubtedly unhappy about the appearance of Europeans, had resolved to not only accept their presence, but exhibited a willingness to share the bounty of North America's natural resources with the newcomers. It seemed that no matter how accommodating the natives tried to be, once Europeans figured out how to survive in the New World, avarice was the predominant European response.
Even though the initial expedition by Columbus began as a search for a shortcut to Asian markets, it was motivated by European greed. The alarming aspect of European exploration was not the motivation that started them, but the apparent and utter disdain for the humanity of the indigenous peoples displayed by Columbus and subsequent European explorers. Each voyage by Columbus contributed to the destruction Caribbean culture. The arrival of the British, Dutch and the French set in motion the decline of other Caribbean cultures and native cultures on the North American mainland. Europeans then introduced the Atlantic slave trade. Importing a labor force to compensate themselves, because the so-called Indians were neither physically, nor psychologically suited to the heavy labor required work plantations or build European styled villages, towns and cities. In providing themselves with free labor, Europeans plundered Africa's most precious natural resource and brain trust. Early Mexican cultures had suffered a fate similar to their eastern brethren at the hands of the Spanish Conquistadors. The natural resources of Mexico, what is now southwestern United States, Central and South America were plundered by the Conquistadors. There can be no justification for one culture to denigrate the humanity of another. However, in their efforts to find new land, resources and markets European rulers unleashed a ruthless colonizing mindset, complete with settlers, soldiers and new weapons, upon the continents of Africa, North and South America. In doing so Europe raised its standard of living, but froze and distorted the development and potential for advancement of three continents.
It is no small matter that both Mexicans and Native Americans were already living here when the ancestors of Jefferson and Madison arrived. It is important to keep their words in mind because they share the same class, if not the politics, as men of John Calhoun's ilk. Calhoun was a man of racist convictions, one of which views he made clear in a speech to Congress in January of 1848, "(W)e have never dreamt of incorporating into our Union any but the Caucasian race-the free white race. To incorporate Mexico, would be the very first instance of the kind, of incorporating an Indian race; for more than half of the Mexicans are Indians...;" (en.wikipedia.org)
It is important to keep the words and the authors of these statements in mind because they represent the prevalent mindset of a government in the midst of implementing their manifest destiny upon the continent of North America. The advent of the policy of manifest destiny placed the U.S. Government on the brink of westward expansion without regard to costs; it would bring the land that had been entirely Mexico face to face with territorial decimation and it would cause Native Americans to teeter on the precipice of annihilation. It could be argued that during the decades following the War of Independence the United States Government was faced with pressures. It had a growing population with rapid increase of European immigration and the custom of raising large families in an agrarian society. There were also periods of economic difficulty after the War of 1812 and during the late 1830s. And of course there was ever present pressure of Southern politicians, who wanted to add slave states or territories to the United States. Militarily the vast lands west of the Allegheny and Appalachian Mountain ranges represented the potential for enormous expenditures of money and manpower to provide defense in the event of attacks from the west. However, the U.S. Government had, without the advice or consent of a single Native American, purchased the Louisiana Territory from France. This purchase gave the U.S. the right to govern the vast stretch of territory between the Mississippi River and the Rocky Mountains. The Native Americans of the Great Plains fell under the same territorial jeopardy as their fellow tribes of the eastern portion of the U.S. with the Louisiana Purchase.
This purchase also gave the U.S. Government the right to parcel out land to European immigrants, free blacks or whomever else it chose. Although the U.S. Government signed many treaties with various Native American groups, it had no compunction about violating those treaties in order to allow settlement by adventurers or prospectors. The U. S. Government legitimized such treaty violations-treaties being the second highest level of law, secondary only to the U.S. Constitution-with claims that the boundaries of freedom and democracy should be preserved only to those capable of self-government. Native Americans were not capable of self-governance in the estimation of the proponents of manifest destiny. Therefore, it would be in the best interest of Native Americans for the U.S. take control of the land.
In the annexation of Mexican lands it could be argued that Mexico's northern territory was under populated and indefensible by a Mexican government in the throes of internal strife. The U.S. could claim that constant warfare with Native Americans made Mexico's northern territory untenable for Mexican settlement and/or governance. Further, it could be argued that the state of Mexican transportation and communication would make it too difficult for Mexico to unify that area under Mexican rule. Hence, it would be in the best interest of both Mexico and the U.S. for the U.S. Government to annex lands that are now the southwestern states of the U.S.
As was mentioned above the introduction of manifest destiny into the psyche of the leadership of the United States' Government signified the beginning of westward expansion of the newly independent nation. The mindset that accompanied westward expansion also contained a not so veiled threat to former colonizing nations of Europe. The newest international power would not interfere with well established colonized populations, who made no attempt to relieve themselves of their domination by European nations. However, the indigenous peoples of the Western Hemisphere could not anticipate European intervention on their behalf, once the bloody implementation of manifest destiny actually began. Hence, territories on northern Mexico, indeed Mexico itself, as well as Native American lands were at risk of being gobbled up and incorporated into the United States. The people of Mexico spent most of the 19
Century at war or engaged in reconstruction. They struggled with Spain and eventually gained independence in 1821. Mexico then spent the next several decades at war with Texas (1830s); the United States (1840s); internal strife (1850s) and then Spain, France and Great Britain during the 1860s. Freedom-loving Mexicans finally overthrew and executed their self-imposed Frenchman Emperor Maximillian in 1867. During these same years the U.S. was experiencing rapid population growth via native births and European immigration, the industrial revolution with advances in communication, transportation and commerce. Therefore, the primitive weaponry and military strategies presented by Native American peoples and Mexicans were no match for the sophisticated weaponry and overwhelming numbers that could be brought to bare by the U.S. in any conflict. The leadership and incredible bravery that existed among Native Americans, while heroic, was outmatched by the U.S. Army's new technology. Even some recently freed from slavery African Americans were duped into helping the U.S. Government to constrain the indigenous people.