Which neutral territory in Europe flirted with making Esperanto its official language before the Germans invaded?
A: Moresnet. This was a sliver of land only 3.5 square kilometers in size:
Here we see:
However, in the early 1900s, several attempts were made to establish Moresnet as a more independent entity. In 1908, one Dr. Wilhelm Molly proposed making Moresnet the world's first Esperanto-speaking state and renaming it "Amikejo" - "place of friendship". A number of a residents learned Esperanto, and a rally was held in support of the idea on August 13th. Apparently almost all the citizens attended!
One can still see many of the stones marking the borders of Moresnet, and there is a small museum in the nearby town of Neu-Moresnet commemorating its history. Moresnet had a not-quite-official flag:
Thanks to the ambitious Dr. Molly, the region also issued its own stamps for a period of 2 weeks, after which local commissioners put a stop to it.
Sources:
In 1990, Fred Dijs made a 48-minute documentary about the rise and fall of Moresnet, Het vergeten land van Moresnet.
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