What is the standard depth of a grave?

Walter Cronkite (who was present as a war correspondent) tells the story of the staff meeting held the next morning to deal with Rundstedt's breakthrough. Patton was a few minutes late. When he entered, conversation stopped. Realizing that he should say something, Patton asked "What do you do when you catch a monkey hanging by its tail?" Answering his own question, he replied "You cut off its balls, and that is what I am going to do with von Rundstedt."