- U-505 (USS Nemo), captured June 1944.
The need for a U/B library in the Atlantic Section of OP-20-G was more than satisfied with the decision to house even the non-crypto and non-communications U-505 documents in OP-20-G, where the secrecy of their source could be best safeguarded. The Atlantic Section assumed the responsibility for translating and disseminating information from Nemo documents under the limitations imposed by the Top Secret classification, subject to the direction of COMINCH (FX-01, Commander Tenth Fleet). The classification of translations which carried no reference either to source or to enemy codes or ciphers was subsequently reduced to Secret.
The processing of Nemo documents was inserted into the Atlantic Section's regular routine for handling U-boat ULTRA intelligence at a time when decryptions of German naval radio traffic had approximately tripled in volume as a result of the wholesale breakdown in German landline communications which came with the Allied invasion of France. Although adequate personnel were not available for an exhaustive treatment of the documents, matters of current interest, including technical documents, were translated and distributed. The speedy exploitation of the documents in the interest of supplementing U-boat ULTRA intelligence was of course OP-20-G's first aim. Priority was given to those items which were of particular concern to COMINCH Combat Intelligence (F-21). Among the items which received immediate attention were the documents on the U-boat grid cipher ("Adressbuch" and "Schlüsselheft F"), standing war orders of COMSUBS, T-V acoustic torpedo, schnorchel, elektra-sonne radio beacons, and radar interception gear.
- Amount of U-505 material.
Approximately 1200 items appear on the catalog of U-505 documents. Two-thirds (800) of these items were made up largely of technical drawings and charts (navigational and grid). The document library was based on the remaining 400
items. The rough classification adopted for the original inventory of these 400 documents showed the items as follows:
Torpedoes 15% Radio communications
(operational & technical)
15% Codes & ciphers 15% Manuals for the CO, orders, etc. 15% Ship and A/C recognition 15% Ships logs, receipts, and papers 15% U/B technical documents
(including periscopes, diesel-electric machinery)
15% Navigation 15% Miscellaneous
- Statement on amount translated.
U/B standing, operational, and current war orders, including appendices: 103
U/B communications war orders: 41
Documents (including technical, schnorchel, elektra-sonne, bold, GSR) and U-505 war diary: 20
- Method of processing.
- Initial cataloging.
- Photographic duplication of selected documents and charts.
- Binding of one photographic copy as duplicate library copy.
- Classification and appropriate library routine.
- Translation from originals according to priority list (concurrently with the above).
- Duplication of translations, distribution.
- Distribution: (Following the initial dissemination of a complete catalog of documents on hand)
- To GC&CS England: photographic copies or originals; grid charts, crypto and communications documents, all technical documents of current interest not already held by Admiralty.
- To F-21 (COMINCH Combat Intelligence): Translations.
- To FX-01 (Commander Tenth Fleet): Translations.
- To OP-16-Z (ONI): Notices of translations available.
- To OP-20: Translations of all U-boat communications war orders.
- To Atlantic and Pacific Fleet headquarters and all US submarine commands: Communications and operational U-boat war orders.
Technical sections of the U.S. Navy received material of interest to them, both in original and in translations, via FX-01 and OP-16-Z.
- Admiralty pinches.
With the Allied invasion of France captured documents became a major business, involving all parts of the Allied organization. As documents were received in England GC&CS kept OP-20-G currently informed via the "Accession lists," with separate listings of German code and cipher material. The Atlantic Section of OP-20-G expanded its library facilities to include a running check on the accessions in England, noting duplications of items already held here from U-505 and
requesting copies of any documents which seemed of particular value, in addition to the code and cipher material which was requested via the Atlantic Section by our cryptanalysts.
- Restoration of Ex-U-852 water soluble documents.
An interesting problem in the exploitation of captured material was presented as the result of the abandonment of a sinking U/B, U-852, in coastal waters in May 1944.
The U-852 was attacked by aircraft on 2 May 1944 in 10°35'N 52°00'E and was closed on 3 May by HMS Falmouth. The burning and sinking U-boat was abandoned by her crew off Cape Guardafui. Eight days later a diver recovered eight secret communications publications wrapped in an ordinary tablecloth. Of the eight documents, five had been printed in water soluble ink on special paper and their contents could be ascertained only from such vestiges of the titles as had not been printed with soluble ink. All documents in the Pinch accession list of 28 May 1944 (received in OP-20-3-GI-A on 21 June) with a notation concerning the disappearance of the text.
Samples of undissolved water soluble paper taken from the U-505 in June were sent by the Atlantic Section of OP-20-G to Army chemists in Arlington Hall (Colonel McGrail). Experiments on the dissolution of text and subsequent restoration were successful in overcoming the closely printed lines of "jammer" in the special paper. The Atlantic Section then requested that GC&CS forward the dissolved U-852 documents, which British experiments had failed to restore.
Although the Army chemists had produced satisfactory recovery of text in the U-505 samples after duplicating the effects of prolonged immersion in salt water, their initial work with the dissolved U-852 documents was disappointing. By straining the eyesight beyond all normal expectations it was possible to distinguish only a few words here and there on the photostatic reproduction of the page which had been subjected to chemical treatment. After several weeks of continued experimentation the resourceful Army chemists hit upon a slight revision of the hitherto "standard" method. A chemical solution was discovered whose action on the dissolved originals was such as to allow a photostatic reproduction which was almost entirely legible, unmarred by the lines of jammer that had blocked earlier efforts. All the material was subjected to the new method and approximately 90% of the text recovered.
Both OP-20-G and the British expressed their pleasure at the final result.
The documents thus recovered were processed by the Atlantic Section in their German form and forwarded together with the originals and photostats to GC&CS. A study of the contents indicated that translations would prove valuable not only to Atlantic Section but also CINCPAC and FRUPAC. Up to this time ULTRA intelligence had not provided complete information on German communications procedure in the Far East. The increasing German interest in this area provided corresponding increase in information via U-boat traffic, but background, including the relation of U-boat communications to surface ship communications, was incomplete. By combining the U-852's "East Asia" documents with the past and current U-boat ULTRA it was possible to set up a fairly complete folder on German Far East communications and keep it up to date. Copies of this revised OP-20-GI-A edition were sent to CINCPAC and FRUPAC.
- Contents of Ex-U-852 documents.
- Communication order for East Asia area with appendices 1, 2, and 3. (The basic order and the first 2 appendices had not been printed in water soluble ink.) Appendices 1 and 2 were brought up to date by ULTRA; appendix 3 was furnished entirely from ULTRA.
- Cipher instructions "Himati" (for surface ships).
- Short signal book "China" (code for surface ships; PPP signals).
- Radio instructions "Kirschblütz" with appendices 1, 2, and 3 for U-boats.
- German-Japanese communication agreement with appendices 1, 2, and 3.
- Cipher instructions "Sumatra." (For joint German-Japanese naval communications. Recovery of the substitution alphabets for "Sumatra" was materially assisted by reading Japanese Naval Attaché traffic.)
- Indicator-group list for supply ships.
- General communications security publication.
Table of Contents
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