When the United States indicated the intention of making common cause with the Allies, 
there was resumption of exchanging scientific knowledge. Sonar and Asdic Scientists became . 
aware that they had paralleled developments and possessed practically identical equipment. The 
primary differences were: British Asdic transducers contained quartz-steel while U.S. Sonar 
had magneto-striction; British Asdic domes were streamlined while ours was a sphere; British 
Asdic ranges were permanently recorded on a range recorder while Sonar ranges were indicated 
on a dial. 
The range recorders are a valuable aid in conducting an attack; we obtained samples from 
Britain and the Sangamo Electric Company started producing our own types. The streamlined 
dome increased the ships speed at which Sonar could be effectively operated from 10 up to 15 
knots; we adopted it from Britain, Canada furnished some equipment, then the Submarine Signal 
Company, the Rice-Barton Company, and the E. G. Budd Company commenced production of U.S. 
equivalents. Britain also furnished some ASDIC Electronic Attack Teachers which provided 
realistic methods of maneuvering models of an Asdic fitted escort attacking an evasive U-boat 
within the confines of a Sonar classroom. These Asdic Teachers added to the growing number 
of Sonar Teachers. 
Thus began a technical liaison which quickly enveloped British.Asdic and American Sonar 
scientists, officers, technicians, etc., into a family known to each other by first names. Research, 
development, ideas, etc., were exchanged, U.S. observers were stationed at British Admiralty 
Anti-U-boat activities, Britain had representatives at U.S. Navy activities, both countries ex- 
changed visits to laboratories, etc. 
The first year of World War Il was a typical blitzkrieg. The Norway invasion in April 1940 
provided more U-boat bases and Italy brought about 100 submarines into the war, 60 were ocean- 
going. The Axis’ use of French ports, starting in July 1940, extended the U-boat s westward 
range. The spotting of approaching convoys by French based aircraft compelled Allied ships to 
take longer routes north of England. The obvious preparations for invading England during 
August of 1940 required British anti-submarine ships to guard the coasts of the British Isles. 
This strategy was timely - Gross Admiral jpoenitz recently stated that insufficient opposing 
German naval strength caused “postponing” the invasion. The diversion of Asdic equipped es- 
corts from convoy duty resulted in U-boats reaching their highest effectiveness - each sinking 
about 10 ships per month. 
At this extremely critical time the British obtained 50 World War I destroyers from the 
United States in exchange for lease of British territory in the Western Hemisphere whiclir we 
used as defense bases. The old “flushdeckers” were equipped with echo ranging Sonar, and a 
hand-picked group of our best Sonar operators instructed British Asdic Ratings in the use of the 
U.S. equipment. Encouragement spread through the Royal Navy’ S anti-submarine fleet; the Asdic 
teams added their range recorders to our Sonar and did very well - one set operated continuously 
from New York to the Irish Sea (21 days) and netted a U-boat. 
By December 1940 the Allies’ original forty million gross tons (about 8,000 ships) had been 
reduced by 4 1/2 million g.t., 1201 vessels, an average of 80 per month, had been Sunk by the 
enemy. About 2500 ships per month had been convoyed by about 600 Asdic fitted escorts of which 
half were oceangoing, the others were small patrol craft. The Germans now had about 45 U-boats, 
an average of 10 operating at sea continually. 27 U-boats and 17 Italian subs had been sunk, 
averaging 3 per month. 
During the winter of 1940-1941 the West Coast Sound School had been expanded and the 
Sound School at Key West established. Courses were given prospective commanding officers of 
anti-Submarine vessels, enlisted men were taught operation and maintenance of Sonar equipment, 
and destroyers were used to train “Attack Teams”. 
The mobilization of the nation’s scientific and technical manpower had resulted in estab- 
lishing the “Office of Scientific Research and Development” (OSRD). The National Defense Re- 
search Committee (NDRC), one of OSRD’s principle agencies, formed Division VI headed by 
Dr. J.T. Tate, which in April 1941 began a thorough investigation of submarine detection on the 
AR A- 2405 
