The files told of the village of Shingle Street being cleared of its residents at 48 hours' notice on 25 June 1940 as a minefield was to be laid near their homes.
Kenneth Clarke, the Home Secretary, ordered the release of the files - which would normally have been closed under the 75- year rule - as part of the Government's endeavour to reduce secrecy.
Residents of the 20 cottages were ordered to leave without explanation. Rumours circulated of beaches 'strewn with charred bodies' which were buried in a nearby forest. One theory was they were German commandos dressed as British soldiers who had stormed ashore, aiming to attack a radar research station.
Another said they were British troops killed when a chemical weapons test went wrong.
Rumours of German raiders inspired Jack Higgins's best-selling book The Eagle Has Landed.