This study on the problems of rear area security is based on German experiences during the Russian campaign. Particularly striking examples have been selected which show most clearly the. type of disturbances created by the Russians, the German countermeasures taken against them, and the lessons learned from experience. The same, similar, or different circumstances were encountered in other theaters of war. Accordingly, a variety of security measures be-came necessary and many new experiences were gathered. Yet, the fundamental questions remain the same everywhere.