DESOTO patrol DESOTO patrols ( DEHAVEN Special Operations off TsingtaO ) were patrols conducted by U . S . Navy destroyer s equipped with a mobile " van " of signals intelligence equipment used for intelligence collection in hostile waters . The USS De Haven is the namesake for these patrols . The " De Haven " performed the first patrol off the coast of China in April 1962 . The first patrol to target North Vietnam in the Gulf of Tonkin was the USS Algerhom in December 1962 . These patrols were initially a response to the Chinese Communists ' unexpected re - definition of their territorial waters to include all waters shoreward from lines drawn tangentially to , and between , twelve mile circles drawn around their offshore islands . Such a declaration represented a huge expansion of their claims . This inhibited the lawful navigation of international waters and increased the likelihood and frequency of formal diplomatic " serious warnings " issued by Beijing when any Seventh Fleet units navigated through these areas . This became a situation to which Commander Seventh Fleet felt compelled to respond . These types of patrols had previously been conducted off the coasts of the Soviet Union , China , and North Korea , but are widely recognized for their role in the Vietnam War . There were three components to the purpose of these patrols . First , they would establish and maintain the presence of the U . S . Seventh Fleet in the international waters off the China coast and later the Vietnamese coast . Second , they would serve as a minor Cold War irritant to the Chinese Communists . Third , they would collect as much intelligence as possible during the patrols . The tactical purpose of the patrols in Vietnam was to intercept North Vietnamese Army intelligence and relay it to South Vietnamese Army forces . With the intercepted communications , the South Vietnamese were able to more effectively coordinate their raids . The destroyers taking part in the DESOTO patrols in Vietnam were accompanied by air support provided by the aircraft carrier ( CV - 14 ) . The DESOTO patrols were part of a larger scheme known as Operation 34A . Run by the Department of Defense at the time , Operation 34A , or " OPLAN 34Alpha " was a top secret program consisting primarily of covert actions against the North Vietnamese . Patrols and SIGADs . The naval Direct Support Units ( DSUs ) based out of The U . S . Naval Communication Station Philippines in San Miguel , Philippines ( SIGAD USN - 27 ) used the SIGAD USN - 467 as a generic designator for their missions . Each specific patrol received a letter suffix for its duration . The subsequent mission would receive the next letter in an alphabetic sequence . Declassified SIGADs . The following table lists the patrols that have been declassified . Gulf of Tonkin Incident . SIGAD USN - 467N specifically designates the DSU aboard the USS Maddox during the patrol involved with the Gulf of Tonkin incident . This patrol was 18th DESOTO type patrol ( each with a Naval Security Group detachment embarked ) conducted since 1962 . On August 2 , 1964 , the destroyer " Maddox " , engaged three North Vietnamese Navy torpedo boats of the 135th Torpedo Squadron . A sea battle resulted , in which the " Maddox " expended over two hundred and eighty 3 - inch and 5 - inch shells , and in which four USN F - 8 Crusader jet fighter bombers strafed the torpedo boats . One US aircraft was damaged , one 14 . 5 - millimeter round hit the destroyer , three North Vietnamese torpedo boat s were damaged , and four North Vietnamese sailors were killed and six were wounded ; there were no U . S . casualties . Post Gulf of Tonkin Engagement . Even after the Gulf of Tonkin incident , the DESOTO patrols continued . On 11 September 1964 the Director of the Naval Security Group , Pacific ( DIRNAVSECGRUPAC ) informed the Director of the NSA ( DIRNSA ) of plans for an intercept team , SIGAD USN - 467P , to be aboard the USS Morton . The patrol was conducted by the " USS Morton " and the USS Edwards approximately one month after the Gulf of Tonkin incident . During this patrol the " Morton " fired upon five fast closing targets , but was unable to confirm the targets visually . Based on radar surveillance the patrol claimed hits on three of the targets .