S E C R E T.  
 
(Equals British MOST SECRET)
 
     
M E M O R A N D U M
 
                                                                                                                                          July 30th, 1943.  
 
From: Lieut. J.S. Plaut, USNR., Naval Section, SCDIC, AFHQ.
   
To: Commander J.L. Riheldaffer, USN(R).
 
     
  SUBJECT:  Report of Proceedings Relative to Interrogation of Survivors of U-409.  
  _______________________________________________________________________________________  
 
ENCLOSURES: "A" Personal letter to Cdr. Riheldaffer, dated July 27th, 1943.
  "B" REcent Information on German U-boats in the Mediterranean.
  "C" INCONSTANT's Action Report.  (3 copies)
  "D" Copy of a memorandum to Lt.Cmdr.Horan, dated July 23rd, 1943.
  "E" Personalia Forms of Survivors of U-409.
  "F" Summary of Notes on Interrogation
  "G" Copy of a Personal Letter to Charles Mitchel Esq. (NID.1/PW) dated July 30th, 1943.
  "H" Nominal Roll of Crew of U.409.
  "I" Documents Recovered from Crew of U.409.
 
 
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  1.        Brief preliminary interrogation of 25 survivors was conducted at Holding Camp 211, the four officers and 4 selected petty officers (ELSER, JANETZKE, ECKHARDT and GODECKE) having been brought directly from HMS INCONSTANT to CSDIC, AFHQ.  Five wounded survivors (WAGNER, MARTENS, GAST, BLUMEL and SCHOKNECHT) was taken directly from INCONSTANT to 94th General Hospital, where they were seen subsequently but NOT interrogated.  GAST and BLUMEL were evacuated to Hospital Camp 127 (ORAN) several days later without our knowledge and counter to instructions.  
     
  2.        The following P/W were brought from Camp 211 to CSDIC, AFHQ for further interrogation HILDEBRANDT, SCHNITZLER, POHL, DAHM, SCHMIDT (Gerhardt), MEYER, PETERS, MANDELKOW and GODRY.  Thus, 17 of the 38 survivors have already been under detailed interrogation.  
     
  3.        Enclosure "E" incorporated data pertaining to the personal history of the survivors and their reaction to interrogation.  
     
  4.        Interrogation of survivors subsequent to distribution of the Preliminary Report dated July 16th, 1943, (CSDIC - AFHQ - N.10) has introduced a number of discrepancies, which as evaluated herewith.  
     
          (a)  Details of U-409.  
 
Radar. It is now believed that Radar may have been fitted in U-409 prior to her 5th War cruise.  This was emphatically denied by all P/W interrogated prior to July 16th, but has been emphasized subsequently by the most reliable informant.
G.S.R. The same informant stated that new G.S.R. equipment, incorporating a "Magic Eye" feature, was fitted in Brest prior to U-409's 5th war cruise.
"Curly" Torpedoes. It is now believed that these torpedoes were fired experimentally by U-409 on one of her war cruises, but that no torpedoes of this kind were carried on her last patrol.  MASSMANN is considered not to have found them adaptable to his tactical methods.
 
          (b)  Sinking of U-409.  
                  Receipt of INCONSTANT's Action REport and subsequent interrogation have established quite conclusively that the destroyer's final pattern of depth charges, set to 700 ft., caused serious water entry in U-409 and forces the U-boat to surface immediately.  Two of these charges apparently exploded directly beneath the boat, which is believed to have been at a depth of about 200 meters.  (INCONSTANT's 700 ft pattern is believed to have been activated at something less than the indicated depth setting, due to changing of pistols).  
          (c)  5th War Cruise (Brest - Toulon).  
                  Subsequent interrogation has revealed that  (1)  U-409 was probably obliged to return to Brest after sabotage of the main ballast tank through the jamming open of a vent with cement was discovered within a few hours after putting to sea;  (2)  Passage of Straits of Gibraltar probably was made at high speed on the surface at night;  (3)  U-409 was definitely attacked by an A/C with M/G fire on the night of June 6th, shortly after entering the Mediterranean.  
     
                                                                                                                 
                                                                                                                         (J.S. PLAUT)  
     
  Copy to:  J.I.C.A. (Naval Section)