Call for Indirect Fire (B2C2497)

Vocabulary and key concepts regarding the procedures, elements, and technical calculations required for Calling for Indirect Fire (CFF) as taught at the Marine Corps Basic Officer Course.

Forward Observer (FO)

The 'Eyes' of the fire support system; responsible for detecting and locating targets, calling for fire, adjusting fire, and relaying results.

Fire Direction Center (FDC)

The 'Brain' of the fire support system; receives the CFF (Call for Fire), computes firing data, and transmits fire commands to the firing unit.

Firing Unit

The 'Muscle' of the fire support system; applies weapon settings and commands from the FDC to deliver rounds to the requested target.

Mil

A unit of angular measurement equal to $1/6400$ of a circle, preferred by artillery and mortars for its accuracy and the mil relation formula.

Degree to Mil Conversion

The process of converting angular measurements by multiplying the number of degrees by $17.8$ (e.g., $90$ degrees approximately equals $1600$ mils).

Mil Relation Formula

States an angle of one mil equates to one meter of lateral distance for every $1000$ meters of range; expressed as $W = (R/1000)(M)$.

Observer Target Line (OTL)

An imaginary straight line from the Forward Observer (FO) through the target.

Observer-Target (OT) Direction

The azimuth from the FO to the target, expressed to the nearest $10$ mils grid and transmitted as four digits.

Observer-Target (OT) Distance

The distance from the FO to the target, expressed to the nearest $100$ meters.

Polar Mission

A target location method where the FO describes the target in relation to their own position; requires the FO to first transmit a POSREP (Position Report).

Grid Mission

The default target location method using the military map grid system; the FO locates the target to a six-digit grid ($100$ meter accuracy).

Call For Fire (CFF)

A concise message in three transmissions containing six elements: (1) Observer identification, (2) Warning order, (3) Target location, (4) Target description, (5) Method of engagement, and (6) Method of fire and control.

Adjust Fire

A type of mission announced when target location is questionable; one gun fires one round at a time until the burst is close enough for the unit to engage.

Fire for Effect

A type of mission announced when the FO has an accurate target location and is certain the first volley will impact the target; all guns fire simultaneously.

Danger Close

Announced when predicted impact is within $600$ meters for mortars and artillery, or $750$ meters for $127 ext{mm}$ Naval Guns.

Improved Conventional Munitions (ICM)

A projectile containing $88$ small grenade-like shaped charges, effective against area personnel targets and armored vehicles.

At My Command (AMC)

A method of control where the FO determines the exact time of fire by announcing "Fire" when ready.

Time on Target (TOT)

A method of control where the firing unit times its fire so the initial round strikes the target at a specific minute past the hour.

Message to Observer (MTO)

The FDC's response to a CFF, which must be read back verbatim and includes: (1) Unit(s) to fire, (2) Changes to the CFF, (3) Number of rounds, and (4) Target number.

Shot

A report transmitted by the FDC after each round in adjustment and the initial round in fire for effect.

Splash

A report transmitted by the FDC informing the FO that the round is five seconds from detonation.

Spotting

The FO's mental determination of a burst's location relative to the target in terms of range (Over, Short, Correct, Doubtful) and deviation (Left, Right, On line).

OT Factor

Calculated as OT Distance divided by $1000$; if distance is >1000 it is rounded to the nearest whole number, if <1000 it is expressed to the nearest tenth.

Successive Bracketing

The range adjustment method used at TBS where the FO establishes a bracket (one round over, one round short) and then splits the correction in half until a $100$-meter bracket is formed.

RREMS Statement

The four items included in the end of mission statement: Refinement, Record as Target, End of Mission, and Surveillance.

Immediate Suppression

A mission used to fire on a target of opportunity that has engaged friendly units; sent in one transmission consisting of identification, warning order, and location.

Creeping Fire

An adjustment method used in danger close missions where rounds are moved toward the target in increments of $100$ meters or less.

What are the three elements of the fire support system?

Forward Observer, Fire Direction Center, and Firing Unit

A mil is a unit of angular measurement equal to 1/?

6400 mils

To convert degrees to mils, we multiply the number of degrees by?

17.8

Why do artillery and mortars use mils instead of degrees?

Accuracy and the mil relation formula’s ability to easily convert angular deviation into lateral distance.

What is North in Mils?

0/6400

What is North East in Mils?

800 mils

What is East in Mils?

1600 mils

What is South East Mils?

2400 mils

What is south in mils?

3200

What is southwest in mils?

4000 mils

What is west in mils?

4800

What is North West in mils?

5600 mils

What are the three methods used to determine observer-target (OT) direction?

Scaling from a map, Lensatic Compass, and Measuring from a reference point

When the FO determines the azimuth to the target (OT Direction) with a compass, the result is in mils ________. Before direction can be sent in a CFF, the FO must apply the _________ in order to convert to mils _____________.

Magnetic, GM angle, grid

Direction should be determined to an accuracy of …. ?

10 mils

True or False?? Binoculars are one of the FO’s best tools to measure angular deviation

True

What are two methods used to determine observer-target (OT) distance?

Estimation, visibility, map study

Distance is expressed to the nearest …. ?

100

What are the two methods of communicating target location?

Polar and grid

The Primary disadvantage of the polar plot method of target location is that FDC must know FO’s ________. The FO transmits this to the FDC is the form of a _______.

position/location, POSREP

With the grid method of target location, the FO locates the target to an accuracy of _______________________ by sending___________________________ digit grid

100 meters, six

IN which methods of target location is the FO’s position not needed by the FDC?

A. Grid, B. Polar, C. A and B

When using the grid method of target location the FO must transmit

Direction

The CFF has ____________________ elements and is sent in ____________________________ transmissions.

three, six

List the elements of the CFF in order

1. Observer Identification, 2. Warning Order, 3. Target Location, 4. Target Description, 5. Method of Engagement, 6. Method of Fire and Control

The first transmission of the CFF consists of _____________________ and ____________________________.

Observer Identification, and Warning Order

The second transmission of the CFF consists of ___________________________________________________.

Target Location

21. The third transmission of the CFF consists of _______________________, __________________________,and________________________________________

Target Description, Method of Engagement, Method of Fire and Control

What method of target location is not announced in the first transmission?

Grid because it is the standard method of target location?

Explain the difference between an “adjust fire” mission and a “fire for effect” mission.

Adjust Fire is announced when the FO decides an adjustment is needed because of questionable target location. One gun fires one round at a time until the round is close enough for the entire firing unit to engage the target. Fire for Effect – announced when the FO has an accurate target location and is certain that the first volley will have effect. All guns of the firing unit fire simultaneously.

In what transmission are “danger close” or a requested shell/fuze combination announced?

Third Transmission

What is “danger close” for mortars and artillery?

600 meters

What would the FO announce if he wanted to control when the firing unit fires?

At my command

What would the FO announce if he wanted the rounds to impact at a specific time?

Time on Target

What type of artillery round contains 88 small grenade-like shaped charges and is effective against area personnel targets and armored vehicles?

Improved Conventional Munition (ICM)

What fuze should be requested for effects against troops in fighting holes or trenches?

Variable Time for artillery/ NSB for mortars

What fuze should be requested for troops in heavy vegetation or with overhead cover?

HE/Delay

What shell should be requested in order to have an incendiary effect on combustible targets such as a refueling station?

HE/WP

What shell is MOST effective for obscuration and screening?

Smoke- M825 (fired by artillery only)

What are the four elements of the message to observer (MTO)?

Units to fire, changes to the call for fire, number of rounds, target number

What should the FO do upon receipt of the MTO?

Read it back verbatim

Unscramble the following information contained in a MTO: (Target #AB2067, B, 2 rounds, ICM, over, MTO).

MTO, B, ICM in effect, 2 rounds, Target # AB 2067, over.

When an adjusting round or the first round in the fire for effect is fired by the firing unit, the FDC announces

Shot, over

What is a “splash”

Transmission that informs the FO when his round is five seconds from detonation.

After the initial round bursts, a ____________________ is recorded and then a __________________________ is transmitted to the FDC in order to adjust the rounds onto the target.

spotting, correction

What are the four possible range spottings?

Over, Short, Range Correct, Range Doubtful