The THOMAS bore down on the enemy, firing point blank, and rammed the U-boat just aft 
of the conning tower, U-233 then sank beneath the THOMAS. 
The 30 U-boat survivors who were recovered offered the following information: In the early 
evening of 5 July, U-233 came up from her usual travel depth of about 250 feet to about 100 feet in 
order to service a torpedo or torpedo tube. Suddenly a high whining sound was heard throughout 
the U-boat followed by propeller noises passing overhead. Depth charges burst all around which 
severely shook the entire boat; glass was smashed, and loose equipment flew all over the boat. 
The boat descended rapidly to about 400 feet at which point water entering the after compartment 
caused her to become stern heavy. A torpedo on the loading rails Suddenly slid into the tube with 
such violence that it disemboweled one of the torpedo men who happened to be in the way. 
Just what happened in the after part of the boat is unknown; not a Single man Survived. The 
U-boat continued to sink by the stern at an alarming angle, was completely out of control, and 
chlorine gas from the after compartment was spreading throughout the boat. Possibly at this 
moment the door between the control room and the diesel room was sealed off. Another pattern 
of depth charges caused further damage. The order was given to blow all tanks and the U-boat 
surfaced. 
As the U-boat reached the surface she was attacked with very accurate fire. The chief 
engineer opened the conning tower hatch and the top of his head was promptly blown off. Succes- 
sive crew members attempting to leave by this hatch added to the pile of dead which littered the 
conning tower. Shells and machine gun bullets tore through the plating around the conning tower, 
and one shell appears to have penetrated the pressure hull and exploded in the petty officers’ liv- 
ing quarters killing everyone and filling the compartment with acrid fumes. 
The 30 survivors who had jumped overboard had left by the forward hatch. Within 15 min- 
utes after Surfacing, the bow of U-233 rose high into the air and Sank almost vertically. 
In the summer of 1943 our efforts in tracking U-boats, routing convoys, assignment of 
“never enough” escorts, use of weapons, methods of attacking U-boats, etc., were centralized in 
the Tenth Fleet created in Washington by the Commander in Chief, United States Fleet with him- 
self as its commander. The existing Atlantic Fleet Anti-Submarine Warfare Unit formed the 
nucleus; NDRC, NRL, Navy Bureaus, ASWORG Universities, and other organizations contributed 
experienced officers, scientists, analogists, technicians, etc. Play-by-play reports of the war, 
received constantly by radio, were fed into IBM machines whose Statistics dictated formulation 
of tactics, doctrines, training, weapon design, etc. Many all-night “coker games” were endless; 
thermos corks popped out black coffee, the chips were U-boats and ships, the betting stakes were 
humanities highest - the Four Freedoms, the cards were face up on an enormous chart showing 
convoys, escorts and U-boats, each play was made with “sweat, tears, and blood’ , and when 
the enemy dealt from under the water - our ace in the hole was Sonar. 
The Tenth Fleet and British Anti-U-Boat Division analysis resulted in increasing the con- 
voy size from 40-50 ships to about 90 without increasing the number of escorts | - their effective- 
ness was increasing. Plane/ship coordinated attacks were improving. Towed “Foxers” or 
underwater noise makers attracted acoustic homing torpedoes away from propellers. Faster 
sinking stern-dropped 300-pound depth charges reduced critical seconds of sinking time during 
which U-boats take evasive action. “Hedgehogs” and “Mouse-traps , mounted on escort fore- 
castles, further reduced blind time by projecting a pattern of thirty-pound charges several hun- 
dred feet ahead, which upon striking the water covered large circular area and exploded only by 
contacting the U-boat thereby indicating a hit which usually results in a kill. The accumulated 
instruments which appended the Sonar and which looked like Christmas tree ornaments had been 
incorporated into the “Console Sonar” which contained new features including: detection of mine 
fields, calculation of U-boat depths with the echo sounder, indication of oncoming torpedoes 
traveling as high as 40 m.p.h., and accessories which indicated to “plot” accurate ranges, bear- 
ings, time to fire weapons, ete. Unescorted fast ships were being fitted with hydrophone torpedo 
detectors; one Merchantman detected anoncoming torpedo, avoided it by turning the ship, then 
rammed and sank the U-boat. 
A- 2405 
=1O= 
