According to reports from Smolensk, the local population has indicated to the German authorities the site of secret mass executions carried out by Bolsheviks, where GPU has murdered 10,000 Polish officers. The German authorities went to the locality of Kosogory - a Soviet health resort situated 16 km west of Smolensk, where they made a shocking discovery. They found a 28 m long and 16 m wide grave containing the corpses of 3,000 Polish officers, arranged in 12 layers. The officers were buried in complete military uniforms. They were partly tied up and they all had wounds in the back of their heads caused by a shot from a revolver. It will not be difficult to identify the bodies because they have become mummified owing to the properties of the local soil and because the Bolsheviks have not confiscated the personal papers of the buried persons. [...] The search for new grave continues and some further discoveries have been made. Under the uncovered layers there are successive layers of corpses. The total number of murdered officers is put at 10,000, which approximately matches the size of the officers' staff of the Polish army, taken prisoner by the Bolsheviks.
Berlin, April 13, 1943
Zbrodnia katyńska w świetle dokumentów (Katyn Crime in the Light of Documents), London 1982