NOTE: This information was compiled from memory and various references, and while I've tried to make it as generic as possible, it is predominately taken from my experience with the Field Artillery in the 1st and 9th Infantry Divisions in VietNam, 1969-1970. Corrections and additions are welcome.
J.M.Hopkins, firstname.lastname@example.org - 06 Dec.1996
ORGANIZATION OF THE FIELD ARTILLERY : (typical 1st and 9th Divisions)
Arty weapons were grouped by caliber and type into "batteries" of 3-6 weapons. Howitzers had calibers of 105mm, 155mm, and 8inch. Guns were 175mm. Mortars were 4.2inch caliber. Smaller mortars (81mm) and 'direct- fire' weapons (106mm recoilless, tanks and 'Dusters') were classed as Infantry weapons and not included in the Field Artillery.
Each battery included the necessary gun-crew for aiming (FDC), firing, handling ammo and maintaining the weapons. Gun-crew members were slanged as 'gun-bunnies', 'lanyard-pullers', 'cannon-cockers', and 'ammo-humpers'.
Batteries were grouped into Battalions, supporting a particular AO within the Division. Batteries included weapons of a single caliber, thus an Arty batallion might consist of several 105mm batteries, a couple each of 155mm and 4.2inch batteries and one or two 8inch batteries, totaling about 60 cannon supported by about 600 personnel.
Each Arty battalion reported to a Division level unit (DivArty) for tactical and strategic coordination within the Division AO. The main task of the Arty in VietNam was to provide support for the infantry in the field. This task was chiefly thru executing 'fire missions' called for by the infantry. Each field unit typically had an Arty-FO (Forward Observer) to provide coordination between the infantry and the supporting arty battalion. Battalion FDC coordinated and formed the liason between the infantry on the ground and the assigned covering artillery battery or batteries.
FIRE MISSION TACTICS: Fire missions in VietNam might be routine, such as marking rounds, night-time defensive target zeroing (DTs), or harassment and interdiction missions (H&Is). The highest priority was given to the 'Contact Fire Mission' in support of an infantry unit in actual contact with the enemy.
When the FO called for a fire mission, he also radioed the target's map coordinates, which the Bn-FDC plotted against his last known position. For routine missions the coordinates were encoded or "Shackled" to prevent any tip-off of the troops' location. Contact coordinates were sent "in the clear" since the enemy troops knew where the friendlies were anyway. In addition, the FO called for a particular shell/fuze combination to best engage his target, and a fire-pattern.
Should he want to shoot within about 70 meters of his own location, he was advised that the rounds would land "Danger Close". The Bn-FDC also assigned a particular battery to fire and confirmed that their take-down of the target coords, shell, fuze and fire pattern were correct. The Bn-FDC gave clearance for the battery to fire and advised any aircraft near the Gun-Target (GT) line to avoid the target area as well as the direct line from the battery to the target.
In the battery FDC, the target coords were plotted and the Deflection (azimuth) and Quadrant Elevation (vertical barrel angle) were calculated using the range to target and recommended powder charge. The lastest MET (meteorological) message was consulted to adjust the aimpoint for temperature, humidity, wind speed and direction.
When the FDC had determined the powder charge to use, the gun crews went into action, pulling the proper shell/fuze combo, 'cutting' the proper powder charge, and setting the fuzes if the fuze was a VT or Time fuze. When the guns were ready to fire the crew signalled the FDC, and the FDC ordered "Battery...Fire" and announced to Bn-FDC and the FO: "...SHOT!" indicating that the rounds were in flight.
Knowing the time-of-flight, 10 seconds before the rounds were due to impact, the battery FDC called "...SPLASH!", signaling the FO to watch for the explosion in order to adjust the impact point on subsequent volleys.
Typical firing patterns might be "One Round", followed by "Battery One" if the initial impact was on target. In contact situations the pattern was often"Battery One, Fire For Effect" at the outset to bring large amounts of ordinance onto the enemy quickly. "Battery One" means that the 6 cannon fire one round in unison, while "Fire For Effect" means that the battery will fire continuously at it's maximun sustained rate, adjusting on the fly, until the FO calls "Cease Fire".
Special missions included "Zone And Sweep" patterns or "Time On Target" tactics for preparing an LZ prior to insertion of assault forces, usually by helicopter.
Zone And Sweep directed the battery to fire a Battery One pattern on the target and also one kill radius beyond, below, left and right of the target, expending 30 rounds, patterning an "X" on the target and surrounding area. Typical kill radius was 30 meters for a 105mm or 4.2inch round, 50 meters for a 155mm and 80 meters for an 8inch round.
"Time On Target" (TOT) was a surprise tactic for devastating a particular target area almost instantaneously. Suspected "hot" LZ's were often prep'd with a TOT mission while the assault forces hovered or circled overhead at altitude. Troops were then inserted into the 'sanitized' LZ before the smoke cleared.
TOT missions involved timing the firing of multiple batteries so that all fire on the same location, with the firing times adjusted to cause the rounds to all impact at the same time. A typical TOT might involve 4 batteries (24 guns), of different calibers; some firing rounds fuzed for ground burst, some for airburst. The effect is that a particular jungle clearing might be quiet and peaceful one second and in the next second be totally enveloped and saturated with explosions in the air and on the ground. Bombardment may cease after the initial volley or be maintained in Fire For Effect mode, creating a sustained saturation of the area with detonations.
Artillery missions also included the firing of parachute flares (Illumination or 'Illum') to provide light at night, Marking Round missions to provide an airburst over a designated map location in order to allow the infantry to take a compass reading and verify their own map location. Harassment and Interdiction missions entailed firing on known enemy trails, hang-outs, etc at random times to keep the enemy off balance. Precision fire missions usually involved one gun firing to destroy a single small target, such as a bunker, abandoned vehicle, or any object to be denied to the enemy. The 8inch howitzer was usually employed for precision missions, being the most precise and accurate weapon in the arty arsenal.
AIRBURST: Explosion in the air, used with Shell-HE to increase the anti-personnel effect of shrapnel thrown off by the explosion, or with Shell-SMOKE to provide a visible 'marking round' in the air above a designated point.
BATTERY: The primary artillery unit, consisting of 3-6 cannon of a single caliber.
BATTERY-ONE: a method of fire wherein the cannon of a battery fire each volley in unison.
CHECK-FIRE: a signal for the artillery to immediately halt firing.
DARMA: Defense Against Rocket Mortar Attack. Artillery tactic to fire against enemy rocket or mortar positions during an enemy attack. Coordinated with Q4 Counter Mortar Radar when available and operational.
DELTA-TANGO: Defensive target, designated by an FO for quick attention if his unit comes under attack. Usually called into Bn-FDC/battery as the infantry established its NDP (Night Defensive Perimeter).
DAISY CUTTER: shell or bomb fitted with a fuze extension to provide detonation 1-6 feet above ground, minimizing the cratering effect and maximizing the blast effect. Used with large bombs (2000 lb) and 6 foot daisy cutter fuzes to create an instant clearing in dense jungle for an LZ.
FAC: Forward Air Controller, a Forward Observer in an aircraft.
FDC: Fire Direction Control. The arty unit which at battery level calculated the adjustments of the cannon to cause the shells to impact on target. At Battalion level, the FDC operated from the TOC (Tactical Operations Center) and provided liason between the infantry, artillery and local ARVN authorities with regard to artillery operations. The TOC often contained an Air Warning group which kept aircraft advised of artillery flight thru the local airspace.
FIRE-FOR-EFFECT: the continuous firing of a battery's cannon, sustained until a 'cease-fire' or 'check-fire' is called.
FO: Forward Observer, travelled with the infantry and coordinated arty missions, or an airborn FAC.
FUZE: Mechanism which causes an arty projectile to detonate (explode).
Various fuzes were available in VietNam to provide detonation above ground, on the ground, or below ground at the discretion of the FO in the field.
FUZE-QUICK: Point-detonating nose-fuze, explodes within .002 seconds after impact, aka:'instantaneous'. The 'standard', most often fired artillery fuze.
FUZE-DELAY: Point-detonating nose-fuze, explodes about .010-.015 seconds after impact, allowing the shell to penetrate the target and detonate inside it. Used to attack 'below-ground' targets such as bunkers and tunnels.
FUZE-TIME: Nose-fuze, detonates after a pre-set time delay; used to obtain an airburst, but will also detonate on impact. Used in VietNam with Shell-HE for antipersonnel effect, or with Shell-HE or Shell-SMOKE as an aerial 'marking round',or with Shell-ILLUM. Not as reliable as FUZE-VT for antipersonnel effect.
FUZE-VT: Nose-fuze, VT designates "Variable-Time". A self-contained radar triggered proximity fuze; detonating within 20 meters of any object in its filght path. Used for reliable 20 meter airburst against personnel targets, although it could trigger on tree foliage or flocks of birds (birdburst). Had adjustable "arming time" to prevent triggering on objects close to the firing battery. Was used for "direct-fire" against ground attack on the battery or FSB by setting a zero-second arming time, causing the shell to detonate within .2 seconds of firing, usually at a distance of 60-100 meters from the muzzle. Also detonated on impact should the radar mechanism fail.
GT-LINE: the direct line on a map from the firing battery to the target. Most ground units avoided travel on the GT-Line since the most common 'mistake' of an arty projectile in flight was the "Short-Round" which fell short of the target, invariably on the GT-Line.
GUN: an artillery cannon with a long barrel. The 175mm gun (M107-SP) was self-propelled, weighed 62,100 lbs and could fire 1 round every two minutes to a range of 32,700 meters (20.3 miles). A long range weapon, it could only fire 400 rounds before its barrel had to be replaced, as opposed to the howitzers which could fire 5000-7000 rounds between barrle refittings.
HIGH ANGLE FIRE: artillery trajectory wherein the shell travels higher than its distance down range. Used for firing over intervening mountains, etc, inherently less accurate than low angle fire (standard) due to shell ballistics and wind effects.
HOWITZER: an artillery cannon capable of both High-angle and Low-Angle fire. The 105mm howitzer was the most commonly deployed type in VietNam, weighed about 5,000 lbs, and could fire a shell 11,500 meters (7 miles) at a rate of 3 rounds per minute. The 155mm howitzer was either a 2-wheeled, towed cannon (M114) or a tracked, self propelled weapon (M109-SP), weighed 12,700lbs (M114) or 52,460lbs (M109-SP) and could fire its shells 14,600 meters (9 miles), at 1 round per minute. The 8Inch howitzer was a self-propelled cannon weighing 58,500lbs and could fire 16,800 meters (10.4 miles), at 1 round every 2 minutes.
MORTAR: crew served, muzzle loading, high angle cannon. 4.2 Inch mortars fired projectiles similar to the 105mm howitzer, HE, WP, Illum, etc. Used primarily for fire missions at ranges too short for howitzers (2-3 Km).
ROUND: Before firing, the assembly of shell projectile, powder charge, and case (105mm), ready to be fired. After firing, refers to the projectile only.
SHELL: The projectile which carries a 'payload' to the target; fitted with a fuze on its nose to trigger its explosion. Payloads included high-explosive, white phosphorus, illumination flares, smoke mixture, 'butterfly' bomblets, or anti-personnel fleshettes.
SHELL-HE: Shell carrying High Explosive. Explodes on the target causing damage by blast effect and by high velocity fragments (shrapnel). Typcally the explosive was cyclonite (RDX), conprising about one half the weight of the shell.
SHELL-WP: Shell carrying white phosphorus. Explodes and scatters burning pieces of phosphorus over the target to cause fire damage, or may be used for the screening effect of the dense white smoke produced by burning phosphorus.
SHELL-SMOKE: Carried a grey smoke mixture; used almost exclusively as a marking round with an airburst fuse. Produced a ball of smoke on detonation.
SHELL-ILLUM: Shell carrying a parachute flare for lighting up an area at night. ILLUM always burst at altitude with a 'soft' ejection charge igniting and pushing the flare out of the rear of the shell body. The flare fell slowly on its parachute, providing illumination, while the shell body travelled downrange and the baseplate of the shell fell somewhat backward along the flight path. Firing ILLUM required the FDC to predict all three impact points in order to prevent injury to friendlies due to falling metal.
BEEHIVE: An anti-personnel, direct-fire shell carrying several thousand small steel darts or 'fleshettes'. Each fleshette is about one inch long and has the appearance of a 1" finishing nail with the nailhead stamped into the form of 4 fins, similar to an arrow. A typical 105mm BEEHIVE has 6000 darts, 3000 of which are loaded pointing forward, 3000 pointing backward. The shell is fired directly at advancing enemy formations similar to an aimed shotgun. At about 50 meters from the muzzle, the round ejects the darts toward the enemy with a medium hard ejecting charge. The forward loaded darts spread into a 45 degree fan traveling forward, while the rear facing darts are forced by their fins to flip around in flight. As the darts flip, they loop away from the GT line, forming a fan of about 60 degrees. Thus 6000 darts fly in a 60 degree fan at about 2000 feet per second toward the enemy. The effect on troops in the open is devastating. Enemy troops about 100 meters from the firing cannon may be pierced by 10-20 darts, those closer may receive 100 or more penetrating stab wounds similar to those inflicted by an icepick.
FIRECRACKER: A 155mm or 8inch shell carrying a large number of golfball sized bomblets which it ejects at altitude over the target area. Upon ejection each bomblet opens canted 'umbrella-like' fins and floats spinning to earth. The fluttering, spinning fall has the appearance of a butterfly in flight. Upon impact a spring on the bottom of the bomblet reacts, throwing the bomblet back into the air and starting a time delay mechanism. When the bomblet rises back to about 6 feet above the ground the delay expires and the bomblet detonates with an energy slightly less than an M26 frag grenade. The effect is that of a low altitude TOT, delivered by one shell. The bomblets exploding in quick succession has the sound, at a distance, of a string of firecrackers.
SHORT ROUND: an artillery round which falls short of its target.
"SHOT!": radio signal from battery to FO that his shells are in flight.
SHRAPNEL: high velocity metal fragments thrown off by an exploding shell. The older shrapnel or 'canister' shell which ejected steel balls toward the enemy was superseded in VietNam by the BeeHive round which projected steel darts.
"SPLASH!": radio signal from battery to FO that his shells will impact in 10 seconds.
TREEBURST: Explosion above ground, usually unintentional, due to a shell striking and detonating on trees or other above-ground-level objects.
VOLLEY: the firing of each cannon in a battery.
WALKING BARRAGE: firing between friendlies and the enemy to provide protection while moving the impact point toward the enemy in order to drive him back.