Each U-boat was “living” long enough to sink 20 ships. When depth charged, they did not break as 
did World War I riveted U-boats, their welded construction provided elasticity and only very close 
or direct hit explosions killed them. They were capable of diving to 600-foot depths. They, re- 
mained at their sea Stations for very long periods as they were being provisioned by “cow” wor 
supply U-boats, each “cow” furnished supplies to about 10 U-boats. The original German “mag- 
netic firing” torpedoes which were designed to be exploded by the target ships influence, proved 
inefficient (Several bounced off HMS NELSON without exploding) and were being replaced. One of 
the new types was designed to explode by impact on the target, another was the acoustic torpedo 
which “homed” itself on the targets propeller sounds, and a third type “looped” within convoys 
thereby increasing the probability of a hit. 
One of the basic reasons for our difficulty was the tremendous shortage of escort vessels 
of which literally hundreds were required to protect the allied communications lines which were 
stretched over thousands of sea miles. Also, the lack of success in individual attacks on U-boats 
was known to be due in part to the need for better training for the thousands of officers and men 
required to man the escorts. However, during that year (1942) all the training ingenuity, ship- 
building skill, and scientific effort had been massed by the Navy to meet the Situation. 
The analysis groups submitted reasons for our poor Successes in attacking U-boats. At 
critical phases Sonar lost contact because: (1) U-boats hearing our pings becoming louder and 
faster, judged the moment of our jattack and therefore went deeper - below the Sonar beam. The 
remedy was the “creeping attack”, delivered by 2 escorts - the first maintaining contact at a 
fixed range and ping interval while coaching the second attacker at very low Speed over the 
U-boat by signals, (2) U-boats created disturbances by backing down, turning sharply, or eject- 
ing chemicals that generated clouds of bubbles, which momentarily reflected strong echoes; these 
echoes Simulated a second or third U-boat thereby confusing the attackers while the hunted 
sneaked off behind his false targets. The counter-measure was to promulgate information by 
radio on this U-boat trick, and to issue instructions to maintain “doppler contact (obtained only 
from moving targets). Sonar -Asdic men soon learned to read through “false” targets; erroneous 
attacks on bubble clouds ceased. 
The Scientific Research Groups submitted certain confirmation of the pre-war work of our 
naval officers and scientists, namely: (1) Sound travelling in warm surface water bends sharply 
downward when it passes through a thermocline (a region where temperature decreases sharply 
with depth) and results in very weak echoes being returned from submarines beneath the thermo- 
cline, (2) That thermoclines may cause loss of Sonar contact, (3) That U-boats may hide under 
thermoclines, (4) That a shipborne, cable-lowered bathythermograph for recording temperatures 
and pressures to locate thermoclines could be used to detect these ocean effects. These confirma- 
tions, and the bathythermograph together with prediction tables and tactical rules were supplied 
to ships for use in the predicting of maximum echo ranges, spacing between escort vessels, and 
interval between successive Sonar pings (Since longer distances require longer time between 
pings). 
The engineering groups had enlisted the aid of another core of manufacturers and fur- 
nished: (1) a gyro-controlled “Maintenance of True Bearing” device to keep the Sonar beam 
directed on the U-boat during an escort S maneuvers or turns; (2) an electronic “Bearing De- 
viation Indicator” scope to indicate visually whether the Sonar beam tended to lose contact due 
to the operator moving the beam either to the right or left of the U-boat, (3) a “Reverberation 
Gain Control” which reduced the heavy reverberations resulting from the Sonar s sudden pings 
which cuase the surrounding water to act like a large empty hall with bad acoustics. This con- 
trol also reduced undesirable interfering echoes from seaweed, shallow water bottoms, tidal 
currents, wakes, etc. 
The effectiveness of the improved Allied anti-submarine measures was demonstrated when 
history's greatest invasion armada of about 1065 assorted vessels made passage in November 
1942 from United States and United Kingdom ports to the coasts of North Africa. Although some 
40 U- boats | were lying in wait, they sank only 23 ships during November. Gross Admiral Doenitz 
observed, “The surprise Anglo -American landings in North Africa called for a concentration of 
U-boats on both sides of Gibraltar. Every U-boat that could reach these waters within 10 days 
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