Atlantic Warfare Today : 431 



of this defensive patrol for tlie bases extended from Newfoundland 

 to Bermuda, into the Bahamas, to St. Lucia, Antigua, Trinidad and 

 British New Guinea. This at once had the effect of moving the pro- 

 tective defenses of the shores of the United States hundreds of miles 

 out to sea. American ships and planes operating from these bases 

 could develop a patrol over the whole western half of the Atlantic 

 basin. When, on their patrols, the planes and warships detected a 

 German submarine, they would naturally notify their respective 

 bases by wireless and there was nothing to prevent the British ships 

 or shore stations from overhearing such reports. 



In April of '41 the United States reached an agreement with Den- 

 mark under which the former became responsible for the defense of 

 Greenland in exchange for the right to construct air and naval bases, 

 and in July Iceland asked the United States to supply them with ade- 

 quate defense, relieving the British who, up to this time, had been 

 providing these services. Under these arrangements, air and naval 

 base facilities were constructed in Iceland. These two agreements 

 again extended the continental defenses. A glance at the map will 

 show that ships operating from these bases could maintain patrol 

 over the western Atlantic far from the American shores in a most 

 effective manner. Patrols of aircraft operating from these bases bene- 

 fited even more in the extension of the area which they had under 

 effective observation. All the effective sea routes were comprehended 

 in these patrols. 



Many developments had come into the field to make submarine 

 defenses more effective. The speed of destroyers and other vessels 

 protecting convoys had been stepped up, their armament intensified; 

 the small but extremely light and fast PT boats had come into the 

 picture; listening devices for the detection of submarines had been 

 greatly improved; a special outgrowth of wireless telegraphy or radio 

 had gradually been nursed into a new device called "radar." 



Way back in the 1920's two young experimentalists. Dr. Albert 

 Taylor and Leo C. Young, working in Washington with high-fre- 

 quency radio signals, had observed that when their instruments were 

 placed on opposite sides of the river the passage of a ship deflected 

 or disturbed their signals. After a little reflection they concluded that 

 such deflection of their signals might be used for the detection of 

 enemy ships passing between two vessels equipped with the proper 

 instruments. No attention was paid to their report but fortunately 

 the building of a new naval research laboratory permitted them to 

 continue their experiments. Later they were involved in the building 



