Operation Neptune was a 1964 disinformation operation by the Czechoslovak secret service, the StB, involving Nazi-era documents. In 1964, the StB publicly claimed to have discovered Nazi-era intelligence files hidden beneath the surface of Černé jezero, a lake in the Šumava, on the border with West Germany. The four chests containing the papers were supposedly discovered during the making of a documentary, in the presence of members of the Western press. In fact the agency itself had placed them there, in collaboration with the KGB.