In the early days of the Vietnam War, US chapter, USAF, USMC, and USN aircraft were unable to deliver ordnance with reasonable accuracy under conditions other than good weather and daylight.  

It became apparent that this was not going to work, especially as the war heated up and many more US forces became involved.  There had to be a way to accurately deliver bombs on targets during bad weather and at night.  

There were two aircraft types that were capable of all-weather day or night bombing. These were the A6 Intruder and the B52 Stratofortress. There were only a few A6's in theater, and there were serious political concerns over using the B52, which was, after all, a nuclear strike weapon.

Out of some sense of desperation, the US government finally overcame its political willies over using the B52 in the war, and the first B52 mission in South Vietnam was flown in 18 June 1965. These early missions were accomplished not by ground directed bombing, but by using the B52’s on board system, the bomb-nav system. The results were not impressive. For example, in the first mission, 27 B52's dropped approximately 1300 bombs into a target box 1 mile wide by 2 miles long. According to the official USA F history, a little more than half of the bombs fell into the target box. The other half obviously didn’t, making it a little rough on anyone in the immediate vicinity, especially if they didn’t need killing and maiming. You know…friendly troops, orphans and school children, hospital patients, those kinds of people. This is somewhat at odds with an AP press release, in which a USAF spokesman reported "pinpoint accuracy."

Strategic Air Command was using a rather simple, and accurate, method of testing the bombing skills of SAC aircrews. This method involved no real bombs. It involved tracking the bomber with what was essentially a modified gun-laying radar, plotting the aircraft track on paper. The bomber crew would signal the point at which the simulated bomb was released. Though a voice indication would work, usually the release point was logged by means of an electronic tone that was turned on some seconds prior to simulated release, and then turned off at the release, causing a break in the recorded track of the aircraft.  

If accurate altitude, ground speed, airspeed, and wind data were provided, a ballistics table for a particular bomb type could be consulted, all that external data applied to the recorded ground track, and a surprisingly accurate score rendered.  

By reversing this scoring process, and tweaking the system to fine-tune its various aspects, a very accurate ground directed bombing system was devised.  

This worked with most bomb types, a notable exception being unfinned napalm. It also worked with just about any aircraft that could drop a bomb, including C130’s and the huge 15000 pound bombs used for clearing landing zones (COMMANDO VAULT).  

Beginning in October 1965, SAC proofed out the system with F100's at the Matagorda Island Range, which was home to Detachment 7, 1CEG (later changed to 1^st CEVG, allegedly to correct the perception that these troops were civil engineers rather than the hard-charging, snake-eating, steely-eyed Air Force answer to Sergeant Rock and the combat happy Joes of Easy Company).  

Ground directed bombing reduced the error considerably, with most sources concurring that Skyspot could deliver within a few hundred feet or less.  The first COMBAT SKYSPOT sites were deployed to Vietnam in March 1966.

Soon ground directed bombing became the much-preferred method of dropping bombs, not only by tactical aircraft, but also the B52’s.  

The program became known as COMBAT SKYSPOT. CSS sites dropped somewhere in excess of 75% of all B52 strikes, which were called ARC LIGHT missions.  There was a once-classified citation for the Presidential Unit Citation, signed by General George S. Brown, which actually showed the percentage at that time as 95%. Unfortunately, I don't have a copy of that document, so you'll have to take my word for it. Or not.

A number of COMBAT SKYSPOT sites were placed in Vietnam and Thailand. Off the top of my head, I can think of these:  

Vietnam:

• Bien Hoa (first operational site, 1 Apr 66, call sign MACON)

• Pleiku  (second operational site, 26 Apr 66, call sign BONGO)

• Dong Ha (fourth operational site, 30 June 66)

• Dalat (fifth operational site, 26 Sep 66)

• Monkey Mountain/Phu Bai (call sign MILKY)

• Vung Tau

• Binh Thuy  (call sign GAP)

Thailand:  

• Nakhon Phanom (third operational site, early June 66; call sign BROMO))

• Ubon (operational some time after Binh Thuy closed; call sign GAP)

• Udorn (call sign LID)

• Mukdahan  (planned site, diverted to NKP)

These were not all operational at the same time.  

Matagorda Island and Detachment 7 became the training school for SKYSPOT crews going over to SEAsia. Later, in the 1970-71 time frame, this training transitioned over to Detachment 50 at Bergstrom AFB, Austin, TX. Matagorda was quite remote, with a host of logistics issues. Moving the school to Detachment 50 greatly improved support for students and permanent party. The training program was called BUSY SKYSPOT. In addition to the SKYSPOT training, Detachment 50 also hosted a TSQ-96 maintenance training course.  

COMBAT SKYSPOT was used in every major campaign beginning in 1966, in Laos, Cambodia, South Vietnam, and North Vietnam, except for operations too far north to allow radar tracking. There was one short-lived but rather spectacular fiasco which involved a more or less undercover operation in Laos – see the references elseplace to COMMANDO CLUB, HEAVY GREEN, and LIMA SITE 85.  

B52’s directed by SKYSPOT sites helped save the Marines at Khe Sanh and Con Thien, and in thousands of other miserable little pestholes and incidents where the lives of our grunts were seriously in doubt, COMBAT SKYSPOT beyond question kept a lot of names off the Wall. No matter one’s individual perspective, whether this was The Right War or something else, this service to our comrades was a good thing.  

COMBAT SKYSPOT sites were used in tens of thousands of missions involving USAF, USN, USMC, RAAF, and VNAF fighters and attack bombers.  

By the time the system had matured, most of the sites were equipped with the AN/MSQ-77. Udorn and Ubon had the AN/TSQ-96. Nakhon Phanom had both an AN/MSQ-81 and an AN/TSQ-96. Nakhon Phanom and Udorn also played roles in the HEAVY GREEN project.  

Later in the war there was considerable doubt as to the usefulness of the bombing, especially in Cambodia. Anyone who was there, and who considers it objectively, comes to the conclusion that we dropped an awful lot of bombs on nothing but empty real estate as part of an area denial scheme.  See also the page for OL-25 at Ubon for more views on the Cambodian bombing. That notwithstanding, COMBAT SKYSPOT was used extensively to relieve pressure on US forces, and to a lesser extent, on ARVN forces. Some of the most spectacular uses included the prelude to the Cambodian incursion, the battle for Skyline Ridge, the relief of beleaguered ARVN forces in Lam Son 719, LineBacker I, Con Thien, Khe Sanh, An Loc, Kontum, and of course numerous battle sites during the Tet ’68 offensive.  

With few exceptions, COMBAT SKYSPOT was not a particularly demanding mission. As the war dragged on and physical conditions improved on the bases where the sites were located , the worst aspects were probably boredom and heat, and separation from family. With few exceptions, crews slept in relatively comfortable hootches on real beds, had real showers, had access to real chow halls, and had many amenities that grunts only occasionally experienced. The sites located on the Thai bases were particularly comfortable. But, there were a lot of repeat tours, and these separations took a heavy toll on families and relationships. COMBAT SKYSPOT tours were six month TDY's, and it was not unusual to find troops with three or more such tours. Add to that the fact that at that time USAF gave no credit for Southeast Asian tours or short tours. So, a fellow who might have three or four SKYSPOT tours within the space of a couple or three years might find himself pulling a year in Korea or some other remote location.  As far as actual combat, that just didn’t happen, certainly not anywhere near the sense we think of it involving patrols, firebases, troop insertions into hot LZ’s, and so on. Bases on which the COMBAT SKYSPOT sites were located were in fact subjected to enemy attack, but these were general in nature. The few casualties suffered were not so much the result of combat operations but rather some tactically naive technicians being slaughtered through stupidity on the part of the command. That doesn’t make it any easier, and it certainly does not lessen their individual courage and accomplishments; but it is nevertheless the truth of the matter.  

Six men were killed on 5 June 1966 near the Dong Ha site, when they sallied forth after refusing accompanying security forces, in order to complete final surveying prior to activating the Dong Ha site:

Losses at Phou Pa Thi, on 11 March 1968 (see links for HEAVY GREEN/Lima Site 85):

24 February 1968, at Gia Dinh:

Lowell V. Smith (TSgt Lowell Vetter Smith is listed in the Vietnam Veterans' Memorial website database. I can find no other information about him. He is listed on the Combat Skyspot Memorial plaque, but is otherwise a mystery, unlike the men who died at Dong Ha and at Phou Pa Thi.)

The last COMBAT SKYSPOT/ARC LIGHT mission of the war was on August 15, 1973, from OL-25 at Ubon RTAB. That involved WHITE cell, a very shaky beacon, a track that looked like it had been laid by a drunken sidewinder, and a target of vague description somewhere in southwestern Cambodia.