The NKVD alleged that, despite German secrecy, it quickly uncovered the plot following a tip-off from Soviet agent Nikolai Kuznetsov, who was posing as Paul Siebert, an Oberleutnant in the Wehrmacht from Nazi-occupied Ukraine. He got the information from an SS-Sturmbannführer named von Ortel, who was known to become "talkative" when drinking.[4] However, other sources state that Hans Ulrich von Ortel never existed, and was a fictional person set up by Russians.[5][6]