Postal censorship for the period 1941-1945 was subordinated to SMERSH (Main Department of Counterintelligence) in the People's Commissariat of Defense of the USSR.
It was the considerations of censorship that changed the address of the letter to the front. At the beginning of the war, it was written as "DKA" (Acting Red Army) "No. (ordinal) PPS (field postal station) regiment number and place of service soldier. Practice has shown that this information greatly facilitated the work of the Abwehr (Army Intelligence of Germany) and refused it. In fact, practice soon showed that such an address system revealed the location of the active part of the Red Army to the enemy. If the Germans seized the mail near the locations of our troops, then it was bad, all the information about their deployment was in front of the enemy as in the palm of your hand.
The officers-operators of the headquarters of the Wehrmacht could only transfer the postal addresses of the Red Army units to their topographic maps. Therefore, the People's Commissar for Defense urgently interfered in the situation, the practice of peacetime proved to be harmful during the war. A new instruction was adopted to address the correspondence of the Red Army in the wartime period, previously there was simply no such.
After the abbreviation DKA. and the number of PPPs was indicated by a special conditional code of the military unit, which was known only to those who read the order to assign the appropriate number to a particular military unit. It should be noted that after June 22, 1941 private correspondence ceased to be a personal matter.
The letters were not sealed in envelopes, but simply folded into triangles and surrendered to the post office in this form. The inspectors (censors) were interested not only in the data contained in the letters about the disposition of units and their numbers, the names of commanders and the number of casualties, but also the emotional mood of the soldiers of the active army.