http://www.espionageinfo.com/Fo-Gs/French-Underground-During-World-War-II-Communication-and-Codes.html"The most famous, and perhaps ingenious security device of resistance groups was the use of a pyramid command structure. The pyramid structure ensured that no member of a partisan group even interacted or conducted operations with more than two other members of the organization. No records of membership were kept, and messages were sent only by word-of-mouth. Each resistance member knew one commanding member and one other partner member. Members kept strict confidentiality, and rarely met in groups larger than their operational units. This structure insured that enemy infiltrators and captured partisans could positively identify no more than two resistance operatives, leaving the rest of the organization unscathed. The strategy worked with some success, until Gestapo agents began to infiltrate the command echelons of various partisan groups.
"The pyramid structure also added an operational advantage as well as security. Ambushes and assassinations of German officers were carried out by a group of three men. One man served as a decoy, the other carried the weapon and shot the victim at close range, while the third member took the weapon after the shooting and walked away from the scene. Often the actual assailants would remain at or near the scene until authorities arrived. As they possessed no weapons, they were cleared of suspicion. Because resistance members in most urban areas did not keep their own weapons as a security measure, weapons used in attacks were returned to their stockpile via courier, often a child, who would seldom arouse the suspicion of Gestapo agents."