In August 1978, Alexander Achenbach, a German businessman who claimed to be the Prime Minister of Sealand, hired a team of German and Dutch mercenaries to seize the abandoned World War II sea fort off the British coast. Armed with weapons, the mercenaries landed by helicopter, taking Michael Bates, son of founder Roy Bates, hostage before claiming control. Upon learning of the invasion, Roy Bates assembled an armed counter-strike team and launched a fast-rope helicopter raid to retake the platform.
The raid was successful, and Bates captured the mercenaries as prisoners of war. While the hired hands were released, Achenbach and his associate Gernot Putz held Sealand citizenship, leading Bates to charge Putz with treason. The West German government was forced to intervene, but the United Kingdom declared it had no jurisdiction over the offshore platform.
Consequently, West Germany sent a senior diplomat from its London embassy directly to Sealand to negotiate Putz's release, which Roy Bates argued constituted official diplomatic recognition of his micronation.