enigmas - and other recovered artefacts - of U-85, The

Cryptologia, Apr 2003 by Hamer, David H

ABSTRACT: Enigmas are recovered from the wreck of U-85 off the coast of North Carolina. Other recovered artefacts include a typewriter and fragments of a codebook.

KEYWORDS: Enigma, Enigma wheels, Enigma M4, codebook, U-boat, U-85, Operation Paukenschlag ('Drumbeat'), USS Roper, Triton, SHARK

INTRODUCTION

Enigma's World War II history is inextricably linked with that of the Unterseeboote. The wreckage of U-85 commanded by Oberleutnant zur see Eberhard Greger, a Type VIIB that sank on 14 April 1942 under gunfire and depth charges from the USS Roper (Figure 1) with the loss of all 46 hands1, lies in approximately one hundred feet of water off Cape Hatteras, North Carolina, at coordinates 35:55N, 75:13W. U-85 was participating in the attacks on merchant shipping along the eastern seaboard of the United States that began in earnest with Operation Paukenschlag [5] on 13 January 1942. U-85 was the first boat lost during these operations2 and was in fact the first U-boat sunk by a U.S. Navy warship in WW2 [8].

On 13 April 1942, U-85 had sunk the Swedish freighter Christina Knudsen off the coast of New Jersey and by that evening was lying on the surface in shallow water off Bodie Island north of Cape Hatteras. Shortly after midnight the destroyer USS Roper under the command of lieutenant Commander Hamilton W. Rowe picked up U-85 on her radar and gave chase [1]. The U-boat was unable to outrun the destroyer and, with insufficient water under her keel to escape destruction by diving, her commander gave the order to scuttle and abandon the vessel. Roper's reaction was to rake U-85 with machine-gun fire killing many of the crew who were jumping into the sea. Those who survived the gunfire died soon afterwards when the destroyer churned through them while they were still struggling in the water and in an incomprehensible act of (literally) overkill dropped eleven depth charges on the already doomed U-boat. Humanity aside, apparently no consideration was given by Roper's commander to the potential intelligence harvest that might have been gathered from the interrogation of survivors or from the recovery of the U-boat's Enigmas, Triton3 keys, signal books and other classified items, all or any of which would have been of inestimable value to those at Bletchley Park who were struggling vainly with the intelligence 'blackout' resulting from the introduction of the four-wheel Enigma only two months earlier. Roper's actions contrast starkly with those of HMS Bulldog and the capture of U-110, almost a year before [7].

For good measure an additional depth charge was dropped on the wreck the following morning by a PBY Catalina aircraft. This was followed by the dropping of two more by Roper in the general vicinity of the wreck. In spite of all of this high explosive, U-85 remained relatively intact4.

At the time of the sinking U.S. Navy divers were unable to recover anything of cryptologic significance, despite attempts to do so [3]. Citing contemporary reports, Blair [1] describes U-85 as ". . . lying nearly flat on her starboard side5. . ." and suggests this as the reason for the failure of navy divers to gain entry to the boat6 despite ". . . about one hundred descents to the wreck." Any consideration of raising U-85 to the surface by pneumatic means was soon abandoned owing to the considerable damage to the boat's ballast tanks caused by Roper's depth charges7.

In recent years U-85 has become a popular dive site for both amateur and professional SCUBA enthusiasts whose modern diving equipment is much less restrictive than that available to the U.S. Navy divers in 1942 and who have opened up additional access points to the boat's interior.

RECOVERY OF ENIGMA WHEELS

Whereas the German army (Heer) and air force (Luftwaffe) had a total of five wired wheels from which to select the three moveable wheels for daily use in their Enigmas, the navy (Kriegsmarine) had a total of eight wheels from which to make this selection8. Since 1 February 1942 the German submarine fleet in the North Atlantic had been using an updated version of Enigma, designated Schlussel M by the Kriegsmarine, which was equipped with an additional, non-moving fourth wheel variously called Zusatzwalze (additional wheel) or Griechenwalze (Greek wheel): this latter cognomen arising from the naming of the two variants of that wheel, 'Beta' and 'Gamma'. Each was paired with a 'thin' Umkehrwalze (reflector wheel), designated B and C respectively. Each combination then formed a variable reflector that could be set in any one of twenty-six positions as part of the internal machine settings. A null position was provided: when set to position 'A' the combination 'Beta/B' had the same wiring as the old 'thick' reflector B so enabling a four-wheel Enigma to communicate with the earlier three-wheel variant. The combination of 'Gamma/C' behaved in similar fashion. The Greek wheels were of an entirely different form from that of the regular Enigma wheels and thus not interchangeable with them [4].