The Field Artilleryman: Instructional Aid Number 43

1. What they did

This is not a research paper but an 85-page instructional magazine of the US Army Field Artillery School, published in 1969, the hundredth year of Fort Sill, Oklahoma. It opens with a short history of the fort’s founding in January 1869 as a base for the US Army’s campaign against the Indigenous peoples of western Oklahoma, in Comanche territory. The magazine’s stated purpose is to keep field artillery soldiers up to date on tactical and technical developments. The magazine was called Artillery Trends until the school was renamed in January 1969.

It carries notes from the school’s departments and the Field Artillery Board, a careers memo, and nine articles: the Mobile Riverine Force in Vietnam’s Mekong Delta; ground surveillance radar in the Delta (“The Big Eye of the Old Reliable”); two articles on the M18 Gun Direction Computer, known as FADAC; a soft recoil howitzer; the Pershing missile; a test of battlefield lighting at night (“Let There be Light”); a radar plotting fan for maps; and a NATO standard for requesting weather data. It closes with lessons learned in Southeast Asia, a list of training manuals, and an index to the 1968 issues.

Several parts deal with seeing and being seen, finding people, and working with maps and grid coordinates, which is why it is in this library.

2. What they found

Seeing at night (illumination test, Fort Sill, 21 May to 1 June 1968)

• Infrared searchlights gave usable light to about 5,000 m (23-inch light) and 7,500 m (30-inch light).
• Ground observers could not tell apart even large military equipment, such as tanks and vehicles, in a lit area more than 4,000 m away, whatever viewing device they used. White sheets were draped over items in the target area when they needed to be told apart. With the 23-inch light used at longer ranges, observers had to stay within 4,000 m of the target, preferably 2,000 m or less.
• The most useful night vision devices were the crew-served weapon night vision sight for ground observers and M18 binoculars for air observers. Under visible lighting, ground observers found the tripod-mounted sight most useful. Passive devices (which use only the light available) were expected to “flood out” under bright light, but this rarely happened, mainly when a user looked straight at a flare.
• Being seen: plotting teams located a lit searchlight in between 55 seconds and 3 minutes 20 seconds, to within 23 to 220 m. The article cautions that these plotters had no other duties and grew more skilled as the test went on. Evaluators looking toward the focused 30-inch beam were almost completely blinded.
• Two searchlights together improved diffused light by 25% (23-inch lights) and an estimated 45% (30-inch lights). Smoke fired behind the target reflected light back onto it and raised the lighting by more than 40%.
• Under diffused light, troops playing the enemy were not seriously affected; those beyond the lit area could see the opposing formations clearly outlined.
• The article notes that darkness has always limited what soldiers can see: observation posts become listening posts at night, telling friend from foe becomes very hard, and shadows can hide enemy forces.

Finding people with radar (Mekong Delta, 1968)

• The AN/TPS-25 ground surveillance radar is rated to detect people walking in the open at up to 12 km. On flat Delta terrain, raised 40 to 50 feet, it produced more artillery targets than any other source. Most sightings were groups of 10 to 30 people moving within an area.
• Whether a moving group was the enemy was decided from the time and place of movement, where friendly forces were, and how close it was to villages. Fire was cleared with local officials to guard against civilian casualties.
• To train and check the crew, a spotter aircraft radioed the grid of farmers, sampans, local forces or water buffalo it saw moving, and the radar crew reported the size and nature of the target; the reverse was also done. The crew was consistently more than 95% accurate in reporting the number of people in a target.
• The radar could also detect movement inside vegetation by day.
• The article stresses that the radar operator alone cannot know what is happening on the battlefield. A small command post told the radar where and when to search hour by hour, using intelligence such as prisoner reports, agents’ reports, captured documents and “market gossip”, with search priority always on the last point of contact.

Maps and plotting

• The radar plotting and capabilities fan is a plastic plotter at 1:50,000 scale, graduated in mils (0 to 6399) around a full circle, with a coordinate scale and a slotted range scale in yards and meters. The article gives step-by-step instructions for plotting a radar position from grid coordinates, drawing a zero azimuth line parallel to a north-south grid line, and polar plotting a point by direction and distance. Plotting directly on a contour map is described as the fastest way to find a target’s altitude. About 75 prototypes had been sent to radar units in Vietnam.
• The NATO standard (STANAG 4103) gives a coded format for requesting weather data for gunnery, including the requesting unit’s latitude and longitude and a code for which eighth of the globe (octant) it is in.

Lessons from Southeast Asia

• Units under mortar fire tended to fire preplanned counter-fire automatically and to neglect crater analysis, which shows the direction the fire came from. The enemy knew the radar’s capabilities and planned attacks to reduce its effect.
• In perimeter defense, flares and illumination rounds expose friendly as well as enemy positions; night vision devices should come first.
• Shell fragments embedded in road surfaces made mine detection almost impossible.
• Under high, dense jungle canopy, forward observers should report tree height so that rounds do not burst in the trees short of the target.

Other subjects

• The Mobile Riverine Force (about 5,000 Army and Navy troops, operational from 2 June 1967) lived on ships and moved by water, because Delta riverbanks were too soft and muddy for vehicles and most dry ground held a house or village. Artillery was fired from barges and from platforms set in 4 to 5 feet of water.
• Notes cover firing tables, computer programs, a soft recoil howitzer (lighter, shorter and faster firing than the standard 105-mm howitzer, with comparable accuracy in tests), and a reorganized Pershing missile battalion.

3. What they concluded

• Darkness will remain a handicap, but new lighting and night vision equipment and tests such as this one are expected to improve night operations.
• Ground surveillance radar used offensively finds more enemy troops than when used only to guard base camps, but it needs a forward command element to direct where and when it searches.
• The radar plotting fan saves time in operation and teaching and can also be used by staff sections, observation towers and other ground surveillance radar crews.
• The floating artillery battalion was the greatest single innovation in riverine operations.
• Fire direction computers have not removed the need for manual checks; good judgement and sound procedures remain the best way to find and correct errors.

6. Other technologies, skills or innovations

• AN/TPS-25 ground surveillance radar on a 40 to 50 foot tower, checked against observers in light aircraft.
• Xenon searchlights (visible and infrared, 23-inch and 30-inch, truck-mounted, towed and helicopter-mounted), and night vision devices: crew-served weapon sight, tripod-mounted sight, individual weapon sight (“starlight scope”) and M18 binoculars.
• Radar plotting and capabilities fan for plotting on 1:50,000 maps.
• M18 Gun Direction Computer (FADAC) with punched paper tape programs.
• Floating artillery barges, helicopter decks on troop boats, and an airmobile firing platform for flooded rice paddies.