At the end of World War I it was found that the A number of U-boats which had actually been sunk was rather less than the number presumed sunk according to the assessment list. At the start of World War II it was intended that the assessment policy be a little more realistic, and more convincing evidence was demanded to secure assessment of "sunk" (A) or "probably sunk" (B).

The Italian surrender was followed by the publication of a list of the Italian U-boats which did not return to base prior to the armistice. When compared with the Allied assessments for attacks thought to have been made on Italian U-boats the agreement was excellent. There were 72 A and 7 B assessments, a total of 79 Italian U-boats sunk or probably sunk, whereas the Taranto list showed 80 submarines to be missing. Furthermore intelligence had provided the names of 67 of them before the armistice, and these names all checked.

The German surrender provided a list of the U-boats lost with the name of the commander and date and position of the sinking. A comparison of the A and B assessments and the losses shown in the German list follows:

Allied assessments compared with German list*
  A B Total German
I   Sept. 39 - June 40 24 0 24 24
II   July 40 - Mar. 41 13 7 20 13
III   Apr. 41 - Dec. 41 26 1 27 27
IV   Jan. 42 - Sept. 42 27 23 50 50
V   Oct. 42 - June 43 79 49 128 144
VI   July 43 - May 44 117 79 196 206
VII   June 44 - May 45 105 54 159 179
  Sept. 39 - May 45 391 213 604 643
* These data are based oil information available at V-E Day. Neither Allied nor German information is complete for the last periods. Hence the figures given here do not agree in detail with those presented in Chapter 8, based on more complete records available several months later. Nevertheless the agreement of allied and German estimates proves the overall accuracy of the assessments made during World War II.

It is clear that the Germans lost more U-boats as a result of Allied action at sea than the combination of A and B assessments would indicate. This is to be expected as losses due to mines, or perhaps ordinary hazards of the sea, would not be known to the Allies. In only one of the periods did the total A and B assessments exceed the losses given in the German list. For this period, July 1940 - March 1941, there were 7 B assessments which have never been confirmed as sinkings though intelligence has completed the story of the sinkings for this particular period. The percentage of B assessments which actually corresponded to sinkings is problematical, but those cases which do not represent sinkings are compensated for by lower assessments which actually represented sinkings though they were not credited as such.

A survey of the attacks on Japanese U-boats shows 38 assessments of A and 62 B assessments, a total of 100 A and B. The individual losses from Japanese lists add Up to 123, of which two were from mines and two by running aground. The agreement is not as good as with the Italian and German lists, but it is still satisfactory, particularly when the greater difficulty of obtaining intelligence is considered.

The A and B assessments for the losses by the three Axis powers are given below and a significant difference is obvious.

  A B Total Enemy Loss
Italian 72 7 79 80
German 391 213 604 643
Japanese 38 62 100 123
  501 283 783 846

The ratio of A to B assessments is very high for Italians, intermediate for Germans, and low for the Japanese. This relationship would seem to be due to at least three main factors:

  1. The Italians gave up easily, surfaced, and surrendered, thus giving sure proof of destruction, Whereas the Japanese seldom surfaced when the game was up.
  2. Intelligence information was easier to obtain from European sources than from Japanese.
  3. Antisubmarine forces in the Pacific had less opportunity to remain in the vicinity to search for evidence of destruction because of other fleet duties.

The complete picture for World War II allows the conclusion that the summation of A and B assessments for attacks on Axis U-boats gives a total which


is close to that of the actual losses and useful for practical purposes. Attempts to correlate B attacks with the loss of individual U-boats were not always successful and showed that the validity of any particular B assessment as evidence of the destruction of a U-boat is questionable.


Table of Contents
Epilogue * Glossary

Transcribed and formatted for HTML by Rick Pitz for the HyperWar Foundation