Question: Who helped Hans-Ulrich von Oertzen develop Operation Valkyrie?
Sentence (from "Hans-Ulrich von Oertzen"): On 26 March 1944, he married Ingrid von Oertzen Langenn, and a selection of 240 letters he wrote to her from 1942 to 1944 were recently published in book form in Germany.
Relevant evidence: No