How extensive the SD's knowledge was about the early plots to kill Hitler by key members of the military remains a contested subject and a veritable unknown. According to British historian John Wheeler-Bennett, "in view of the wholesale destruction of Gestapo archives it is improbable that this knowledge will ever be forthcoming. That the authorities were aware of serious 'defeatism' is certain, but it is doubtful whether they suspected anyone of outright treason."[108]