This article by Gideon Rachman at Financial Times makes it clear that annexation has returned to the foreign policy scene:
A recent opinion poll for the Pew Research Center reveals that startling numbers of Europeans are not satisfied with their nation’s borders. Asked whether there are “parts of neighbouring countries that really belong to usâ€, 67 per cent of Hungarians replied in the affirmative, as did 60 per cent of Greeks, 58 per cent of both Bulgarians and Turks, 53 per cent of Russians and 48 per cent of Poles. Such sentiments even lurk in western Europe — 37 per cent of Spaniards, 36 per cent of Italians and 30 per cent of Germans also agree with the statement.
In normal times, these kinds of ideas would not matter much. Hungarians, for example, can bemoan the 1920 Treaty of Trianon, which, as they see it, resulted in the loss of two-thirds of Hungarian land, without believing regaining that territory is a practical idea. The danger is that these are not normal times. The idea of annexation — long taboo in international politics — is creeping back into the global political discussion.
China’s annexation of islands in the South China Sea, Russian seizure of Crimea, Israeli plans to annex parts of the West Bank, there are dozens of other plans, threats, and initiatives already under way.
IMO what all of this indicates is the end of the Pax Americana. A little less than 30 years ago the U. S. denied Saddam Hussein’s annexation of Kuwait. Since then a series of feckless trade and foreign policy decisions have resulted in, at least, a relative decline in American power which is allowing long-festering resentments and nationalistic plans to bubble to the surface all over the world.
How serious can annexation sentiments be if the majority of the countries listed won’t properly fund their militaries?
That argument could be made about Hungary but certainly not about Greece. And it clearly isn’t true of Russia, China, or Israel.
Hungary’s borders prior to 1920 included a large number of ethnic minorities, especially Germans and Rumanians. As a result the Magyars were practically a minority in their own realm. The 1920 treaty reduced Hungary to its Magyar-dominant territories except for an enclave near the Carpathians.
Not mentioned is the irredentist nature of ISIS, whose first step towards world conquest once they had absorbed all extant muslim nations under the black banner was the recovery of the Balkans and Al-Andalus (Hispania).