Cases where racial, ethnic, and/or religious groups ended up becoming huge minorities due to border changes?

[Futurist]

Other than the post-World War I territorial changes (which resulted in large German and Hungarian/Magyar minorities ending up in neighboring countries) and the post-Cold War territorial changes (which resulted in large Russian, Serb, and Croat minorities ending up in neighboring countries), which additional cases were there where racial, ethnic, and/or religious groups ended up becoming huge minorities due to border changes?

(The World War II-era border changes I will not count for the purposes of my question here if they were not made permanent--and some of them weren't made permanent, such as the cession of Northern Transylvania to Hungary, which was reversed by the victorious Allies after the end of World War II.)

Personally, I could think of Turks in the Balkans, Middle East, and North Africa who became minorities during the 19th and/or early 20th centuries due to huge Ottoman territorial losses, but who else would actually qualify for this?

[Futurist]

How could I forget? Poland after the late 18th century Partitions of Poland. Poles I would presume were a majority or at least a plurality in the Polish-Lithuanian Commonwealth, but then they ended up becoming minorities in Prussia, Austria, and Russia.