Throughout medieval and modern history, nations have sought to reclaim lands they or their allies were forced to cede. There are many examples. A few of them are: Crusades were fought to reclaim “The Holy Land” for Christendom; Hitler began his rampage by invading countries that had taken German lands following WW1; Argentina fought the British, attempting to reclaim the Falklands; Iraq sought to reclaim Kuwait, claiming Kuwait was a natural part of Iraq, lost in the Anglo-Ottoman Convention of 1913; Today, the longest running example, in modern history, of armed conflict to regain territory, is along the borders of Israel.
In a treaty, signed in 1848 between Mexico and the United States, ending the Mexican-American War, Mexico lost claim to all lands north of the Rio Grande, meaning Texas, and all lands in states now known as: Arizona; California; Colorado; New Mexico; Nevada; Utah and Nevada.
Given the history of nations seeking to reclaim ceded territories, it is not surprising or unusual to think that Mexico would desire the same. In fact, it flies in the face of history to think otherwise. However, it would be sheer foolishness, for Mexico to attempt a military invasion of the the world’s greatest super-power. But it is possible they learned a lesson from their own history.
Following Mexico’s War of Independence, settlers from countries other than Mexico and Spain were invited to Texas. It took less than ten years for the Mexican government to realize their error and prohibit immigration from the United States. However, by this time, residents of Mexican descent were outnumbered by more than 4 to 1 and the fires of independence were burning.
Allowing unchecked immigration led to Mexico’s loss of Texas and the same is happening today across Europe. Muslims there have increased in numbers allowing them to control large geographic areas, both physically and politically. London has a Muslim mayor and Sharia Law is being recognized in their legal systems. Without firing a shot, Muslims are changing the religious and political economies across Europe because of unchecked immigration and their refusal to assimilate. Like it or not, Muslims are doing the same in the U. S.
The lessons of history are not lost by people that pay attention, they are only lost by people that think they are above history. Mexico seems to be paying attention. Why would they allow a seemingly endless stream of people, from south of their border, to trek across the full depth of their country, while aiding and abetting them?
Perhaps, Mexico desires to see these Spanish-speaking people enter the U. S. because they know a common language binds people together; They know from their own history that it is possible to take control of a country through immigration; They know that supplying the required numbers of immigrants from their own people would disrupt their own society and economy; They know that facilitating sufficient numbers of Spanish-speaking people from outside their own country, to invade the U. S. will allow them to re-take lost territories without firing a shot or supplying the manpower.
Mexico probably has little interest in regaining sovereign control of its lost territories. They do not want to build a fence between the Southwest and the rest of the U. S. They are happy to leave government and the expenses thereof to the U. S., while they receive the windfall that comes when they control the economy.