<P> Ahead - throwing weapons including Hedgehog and Squid raised the percentage of kills by British surface ships (1943--45) from 85 kills in 5,174 attacks (1.6%) for depth charges to 47 in 268 attacks (17.5%) for Hedgehog, the success rates rising with time . </P> <P> Detection by radar - equipped aircraft could suppress U-boat activity over a wide area, but an aircraft attack could only be successful with good visibility . U-boats were relatively safe from aircraft at night for two reasons: 1) radar then in use could not detect them at less than 1 mile; 2) flares deployed to illuminate any attack gave adequate warning for evasive maneuvers . The introduction of the Leigh Light by the British in January 1942 solved the second problem, thereby becoming a significant factor in the Battle for the Atlantic . Developed by RAF officer H. Leigh, it was a powerful and controllable searchlight mounted primarily to Wellington bombers and B - 24 Liberators . These aircraft first made contact with enemy submarines using air - to - surface - vessel (ASV) radar . Then, about a mile from the target, the Leigh light would be switched on . It immediately and accurately illuminated the enemy, giving U-boat commanders less than 25 seconds to react before they were attacked with depth charges . The first confirmed kill using this technology was U-502 on July 5, 1942 . </P> <P> The Leigh light enabled the British to attack enemy subs on the surface at night, forcing German and Italian commanders to remain underwater especially when coming into port at sub bases in the Bay of Biscay . U-boat commanders who survived such attacks reported a particular fear of this weapon system since aircraft could not be seen at night, and the noise of an approaching aircraft was inaudible above the din of the sub's engines . Subsequently, the common practice of surfacing at night to recharge batteries and refresh air was mostly abandoned as it was safer to perform these tasks during daylight hours when enemy planes could be spotted . A drop in Allied shipping losses from 600,000 to 200,000 tons per month was attributed to this device . </P> <P> By August 1942, U-boats were being fitted with radar detectors to enable them to avoid sudden ambushes by radar - equipped aircraft or ships . The first such receiver, named Metox after its French manufacturer, was capable of picking up the metric radar bands used by the early radars . This not only enabled U-boats to avoid detection by Canadian escorts, which were equipped with obsolete radar sets, but allowed them to track convoys where these sets were in use . </P>

Where was the battle of the atlantic fought