1. Oberlander, Helmut: 1
  2. occupation zone: 1, 2
  3. Oggins, Isai: 1, 2
  4. OGPU (United State Political Directorate): 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18
  5. Ohlendorf, Otto: 1, 2
  6. OKR Smersh: 1, 2, 3
  7. Okulicki, Leopold: 1
  8. Olsky, Yan: 1, 2, 3
  9. OO (Special Department): 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51
  10. Operation Ariitsy: 1
  11. Operation Barbarossa: 1, 2, 3
  12. Operation Flamingo: 1
  13. Operation Monastyr’: 1
  14. Operation Zeppelin: 1, 2, 3, 4
  15. Order No. 1: 2, 3, 4
  16. Order No. 1: 2
  17. Orpo (German Order Police): 1, 2, 3
  18. Osetrov, Nikolai: 1, 2, 3, 4, 5
  19. OSO (Special Board): 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26
  20. osobist (OO officer): 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14
  21. OSS (Office of Strategic Service): 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
  22. Ostashkov: 1, 2
  23. OVD (Department for Especially Important Cases): 1, 2
  24. Oxley, Walter H.: 1