This translated German document provides general comments on the E-boat operation.
Abbreviations: OIC (Officer in Charge) E-boats = F.d.S. = Führer der Schnellboote S147 etc = German designation of the E-boats
German Comments on Operation
28th April, 1944 – Scheveningen
As subsequent analysis by the Observation service showed, the eastern convoy had already passed the Bill of Portland at 2100h. The targets detected at BF 2172 center left side, course 80 degrees, at 0020h, therefore presumably were the WP-convoy or following escorts.
The flotilla came upon a landing training group which was only covered by destroyers at a distance, which the boats were able to pass almost without resistance. The enemy’s main defenses were open along the course of arrival southeast to east of the Bill of Portland.
Not even the fact that the boats had already been detected an hour before encountering the target had not led the enemy either to concentrate its defenses on the land defense group [is landing training group meant here?] or to withdraw it from the attack area. The attention of both the naval forces and of the detection equipment apparently was concentrated on the eastmost E-boat group, which attacked the two presumed destroyers and torpedoed one of them. The boats took advantage of the minimal security of the group, with good results.
The landing training group was broken up and sailed around relatively helplessly. One can see how ponderous, poorly maneuverable and poorly coordinated such groups are. On the return route, the 9th E-boat flotilla surprisingly came upon an isolated group of LCTs, which were being guarded by patrol boat PC 74. At about the same time the 5th E-boat flotilla sighted 3-4 destroyers, which had been called from an ambush position off the coast of Brittany to ward off the E-boats. It was the ”Force 27”, which consisted of at least four modern destroyers and has been observed primarily in offensive advances.
The fact that our boats suffered no losses is to be attributed to the successful element of surprise.
Concerning the success of the operation, the Observation service reports the sinking of 2 American LSTs and the torpedoing of an LCT. The torpedoed LCT was probably taken to Dartmouth. From the number of survivors and recovered bodies it can be concluded that the vessels carried landing personnel on board. In various radio messages mention is made of 100 to 150 survivors or dead.
The sinking of the destroyer south of the Bill of Portland cannot be confirmed from the radio reports. Confirmation can only take place after thorough study of the encoded material which is still being received.
The boats of the 5th E-boat flotilla last night shot 8 coordinated single torpedos, each with 2 T I with TZ 3 [TZ appears to refer to a torpedo ignition type] and Magnetic Ignition I, depth setting 4 meters. Out of four of the pairs of coordinated torpedos, one each struck the target with a strong detonation, a 40 to 70 m high column of explosion and a bright flame. When the hit struck the destroyer, the sinking could not be observed due to defensive fire; the second hit in the stern of the steamer of 1500 GRT led to sinking within 10-15 minutes.
The torpedo from S138 which struck the destroyer also led to co-detonation of two coordinated single shots from her partner ship S136. S136 had fired at the front destroyer in the group about 20 seconds later, using the same firing settings. Range ca. 2200m, distance between E-boat pairs approx. 100m. The co-detonation of S136’s hit was reported as 1000m. It was not observed that S138’s shot which missed the target detonated along with the hit.
Even though the TZ 3 ignition offers advantages over the normal trigger thanks to its effectiveness at the target, its disadvantage, the excessively high level of co-detonation, has appeared again. In the 5th E-boat flotilla’s operations of 1/6/44, a double shot either co-detonated or detonated by itself due to the heavy swells. In this operation two coordinated single shots fired at a destroyer with relatively safe firing settings co-detonated. In view of the results of this test on the front it appears that deployment of the TZ 3 ignition is only justified against shallow targets for which the success of impact ignition is doubtful.