The government in South Africa is currently in the process of seizing land from white farmers. Using the pretext of reversing the legacy of imperialism, thousands of people who have lived on their land for their entire lives find themselves uprooted and uncertain about their future, with their land redistributed to black farmers. This is not the first time whites in Africa were displaced by the government - Robert Mugabe of Zimbabwe made the same decision which lead to severe agricultural hardship, while neighboring Zambia brought in displaced whites and successfully used incentives to invest their capital into farms.
How the events in South Africa will fully unfold has yet to be seen, but revanchism - the desire to reclaim lost territory - has a long and storied history. In the earliest days of humanity we wandered across a borderless world, pursuing our prey or escaping inclement weather. Over a period of tens of thousands of years, humanity began the process of permanent settlements. And while tribal or national identity changed over the subsequent thousands of years through natural genesis, assimilation, or depopulation and repopulation, these settlements - and the lands that surround them - became a matter of identity for the people that lived there.
Damascus is an excellent example. Damascus is considered one of the oldest continually populated cities on Earth - and with a pedigree of 11,000 years of habitation, it might be the oldest. The city of Damascus has been populated by Aramaeans, Hittites, Egyptians, Assyrians, Greeks, Romans, Rashidun, Umayyads, Abbasids, Fatimids, Seljuks, Ayyubids, Mamluks, Ottomans, French, and is currently controlled by Assad's Syria.
What would happen if every aforementioned group claimed that Damascus was theirs? The desire to take back land that you feel belongs to your ethnicity or nation is known as revanchism. The clear problem is that all parts of the globe have, at one time or another, been controlled by different groups of people. Inevitably, someone's claim to an area is only as good as their ability to utilize force to seize control. As such, revanchism has been fuel for several conflicts, especially as we have moved into the era of modern national identity.
Alsace-Lorraine, also known as Elsass-Lothringia, is a piece of land that has changed hands between France and the Holy Roman Empire/Germany several times throughout history. Notably seized by a victorious Prussia after embarrassing the French in the 1870's, it became a rallying point for the French 40 years later during World War I. Awarded to France after Germany's surrender, the Nazis would later assimilate it back into the German domain after successfully invading France in 1940. After the Nazi defeat, this bloodstained chunk of land was given back to France, which controls it to this day. Germany has made no overtures to take it back, nor any other territories lost at the end of the World Wars. Germany, at least, has learned the cost of revanchism.
The ongoing conflict in the Levant concerning Israel and Palestine is another focal point of revanchism. Citing biblical-era claims to the region once known as Canaan, Israel was reborn in the spirit of Jews returning to their homeland, a rejuvenation of the Jewish state that had existed for over 500 years. This was not that desirable to the Muslims and Christians that were already living there in 1947, and had been living there in greater abundance while having governments adhering to their faith intact for longer periods of time than the ancient Kingdom of Israel. Disagreement of who has legitimate claim to Canaan is a modern Gordian knot, and it seems more likely to end in ethnic cleansing than not.
The southwestern United States is another area with revanchist phantoms. After Texas declared independence, it was admitted to the United States. This predicated the Mexican-American War, where a decisive American victory led to the United States taking control of almost half of Mexico's territory, which corresponds to the whole or part of modern California, Arizona, New Mexico, Utah, Colorado, Nevada and Wyoming. It is important to recognize that territorial transference was the modus operandi of a victor in a war for most of history, making its efforts worthwhile; in the post-World War II era self-determination is seen to overrule expansion by conquest.
As this took place roughly 100 years before World War II, the victor took the spoils. It has been 170 years since the Treaty of Guadalupe Hidalgo, and many generations of people have lived and invested in the framework set up by the American government in this area. This is seen as irrelevant to some members of La Raza, who consider the American seizure of its southwest illegal and demand its return to Mexico. These voices are promoted by American white supremacists and nationalists, who play up the possibility of a Mexican invasion or revolt to embolden their supporters. The idea of the Mexican government declaring war on the American government to take back the cession is absurd, but a division of loyalty by American residents of Mexican descent would not work in the favor of the United States.
The current conflict in Ukraine uses revanchism as a casus belli for Russians. The Crimean peninsula was fought over between the Russians and Turks for centuries, and when the Russians definitively took control of the area, they made it the center of the Black Sea fleet - an achievement for a nation obsessed with finding a warm water port. Control of this area was of the same critical importance for the Soviet Union, but when Nikita Khrushchev was leading the USSR the Crimea was administratively transferred from Russia to Ukraine. As long as Ukraine was solidly inside the Russian sphere, its Black Sea fleet would still have a base.
But after the Euromaidan revolt and the expulsion of President Viktor Yanukovych, the possibility of yet another Eastern Bloc nation joining NATO, particularly one that borders Russia and could expel or sink the Black Sea fleet, was too much for Putin to handle. Hence, the it's-not-an-invasion-it's-a-revolt of the Crimea and the Donbass commenced, using the excuse of protecting Russians living inside these areas. This has caused considerable worry in the Baltic states of Estonia, Latvia and Lithuania, which all have sizable Russian minorities. This conflict has yet to be resolved, but Ukraine can certainly not withstand an unrestrained Russian incursion.
Taking all of this into account, if someone is to claim that an ethnicity or tribe has absolute claim to a plot of land, what timeframe should be used to assign that land to that people? For example, Russia currently occupies a chunk of land on the Baltic coast called the Kaliningrad Oblast. This was seized from Germany after World War 2. This parcel of land was the core of Prussia, which was the state that unified Germany in the first place. Is that rightful German land? Does the fact that this land was settled by Germans at the expense of Old Prussians, who were ethnically cleansed by the Teutonic Order, undermine that claim? Should it be controlled by the Lithuanians, who are ethnically closest to the Old Prussians?
Whatever year you want to base a people's claim off of, that will come at the expense of others who hold that land today. They will reasonably enough question why that particular year was chosen; after all, such a restructuring would undermine property rights, contracts, and families for all within that land. It seems like the most reasonable and peaceable position to take is going to be keeping borders as they are, while countries do not make themselves nation-states and instead enable all within their borders to be treated equally as citizens.