Here’s a good story. True one, too.
Immediately following the Armistice that ended the first world war in 1918, allied troops occupied the western bank of the Rhine and established bridgeheads on the eastern bank to prevent German access to raw materials and industrial infrastructure in the Rhineland.
One in Cologne (British, one in Koblenz (American) and one in Mainz (French), each with a radius of 30km and overlapping to cover the entire east bank of the river.
That’s what they thought.
The American and French sectors didn’t overlap, leaving a bottleneck-shaped strip of land that was cut off from unoccupied Germany, with no road, rail or ship services.
They declared themselves a Free State in 1919 , issued their own passports, currency and stamps and justified smuggling as the only alternative to starvation. Hijacking coal trains was a popular pastime.
This lasted 4 years until the French occupation of the Ruhr and before they could establish an embassy in Berlin and diplomatic ties with other countries.
More here (Told you it was true…)