The Principality of Sealand is a micronation off the east coast of England claiming to be an independent country. Found on a World War II sea fort, Sealand was ruled by its founder until his death in 2012 and even experienced an attempted coup in 1978.
After a business proposition went sour with a German businessman who had invested in Sealand and acted as its Prime Minister, the German businessman attempted to stage a coup with a band of hired mercenaries seizing the founder’s son hostage on the sea platform.
In retaliation, the founder launched a counterattack, freeing his son and taking the German businessman’s lawyer hostage. After an intervention by the British and German governments, the dispute was resolved with the German businessman forming a “rebel government” in exile which still exists.