Although Tukhachevsky's prosecution is almost universally regarded as a sham, Stalin's motivations continue to be debated. In his 1968 book "The Great Terror", British historian Robert Conquest accuses Nazi Party leaders Heinrich Himmler and Reinhard Heydrich of forging documents that implicated Tukhachevsky in an anti-Stalinist conspiracy with the Wehrmacht General Staff, to weaken the Soviet Union's defence capacity. These documents, Conquest said, were leaked to President Edvard Beneš of Czechoslovakia, who passed them to Soviet Russia through diplomatic channels. Conquest's thesis of an SS conspiracy to frame Tukhachevsky was based upon the memoirs of Walter Schellenberg and Beneš.