DESOTO patrol

DESOTO patrols (DEHAVEN Special Operations off TsingtaO) were patrols conducted by U.S. Navy destroyers 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 USS Ticonderoga (CV-14) (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 boats 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.