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    RTO Indirect Fire Support

    Chuck Yeager


    DISCLAIMER: I have created this guide over a long period of time and it has undergone a lot of changes. As this covers communications, this guide is part of RTO. It is advised that people playing mortar also give this a read. This guide has been reviewed and approved by the Mortar trainer. If you have ANY suggestions, feedback or criticism, please let me know, but only through PM. That way I can alter this guide if necessary, and this way we will have only one visible guide as an up to date reference instead of a discussion because we all have our individual take on things.



    The RTO is the officer that is responsible for communicating between ground assets and platoon (both Platoon Lead and squad leaders). When a mortar team is being used, the RTO will give fire missions to the mortar team, most of the times operating as an observer. These fire missions can be requested by other squads on 69, or can be directed by RTO himself.

    Potential call signs: RTO / Loki / Rain Maker

    Mortar team

    A mortar team consistently has two positions; loader and gunner. Besides the task package that goes with each name, the loader is also in charge of communicating with RTO and making all the calculations (see the FK mortar guide).

    Potential call signs: Hammer / Thor / Steel Rain

    Forward Observer

    The Forward Observer (FO) is an optional role and is not always viable in a mission. The FO observes the enemy from the front line or overwatch positions and will communicate directly with the RTO to request fire missions. The FO is purely a scout that has knowledge of the capabilities and restrictions of the available indirect fire support. An FO can be part of Platoon HQ or can be embodied in a Squad. Most missions, squad leaders will function as FO.

    Call for Fire

    Every fire mission follows three steps. The RTO (from here on called observer) will initiate communications and will require the mortar team to repeat the entire fire order for verification.

    1. Observer identifications and warning order
    2. Target location
    3. Method of fire


    “STEEL RAIN 1-1, this is RAIN MAKER. FIRE FOR EFFECT, grid 015 025, 1 times HE, AT MY COMMAND, OVER.”

    “RAIN MAKER, tis is STEEL RAIN 1-1. FIRE FOR EFFECT, grid 015 025, 1 times HE, AT YOUR COMMAND, OUT.”

    1. Observer identification and warning order

    The observer will initiate radio communications, using their call sign to address the recipient. Along with the identification, the mission type will be communicated as well.

    The possible mission types are the following:

    • Fire for effect
    • Adjust fire
    • Immediate suppression
    • Immediate smoke

    Fire for effect

    When the observer is certain that the target location is accurate and that the first deployed round should have the desired effect on target, he announces FIRE FOR EFFECT.

    The observer should always try to gather the needed information for the first round to be FIRE FOR EFFECT.

    Example: “STEEL RAIN 1-1, this is RAIN MAKER, FIRE FOR EFFECT.”


    Adjust fire

    When the observer wants to make an adjustment to the previous fire mission (incorrect target location or other reasons), he announces ADJUST FIRE.

    Example: “STEEL RAIN 1-1, this is RAIN MAKER, ADJUST FIRE.”

    Immediate suppression/smoke

    When friendly troops or assets are being engaged, the observer can request an immediate suppression/smoke fire mission. The observer announces IMMEDIATE SUPPRESSION or IMMEDIATE SMOKE, followed by the target location. The mortar team is allowed to deploy rounds as soon as they are calculated and loaded. This type of fire mission is mostly used when having pre planned targets, such as known hostile emplacements or mission objectives.

    Example: “STEEL RAIN 1-1, this is RAIN MAKER, IMMEDIATE SMOKE.”

    2. Target location

    Being able to correctly calculate (and communicate) the correct target location is vital for a successful fire missions. To determine the target location, three methods can be used.

    • Grid reference
    • Target mark on map
    • Shift from known position

    The most recurring method will be “target mark on map”.


    Grid reference

    Using the grid system, you can relay coordination markers quickly to fire support. Use the vertical and horizontal grid lines on the map to determine a 6 digit grid (example: 035 034). If extreme accuracy is required, an 8 digit grid will be advised.

    Numbers should always be pronounced in its single form. In the given example the communication would be ZERO THREE FIVE, ZERO THREE FOUR (035 034).


    Target mark on map

    If the observer is able to pinpoint the target on the map, he should try and place a marker on its exact location. Map marker SIERRA is reserved for Fire Support (example: marker “S1”). It is preferred not to use common markers such as X1 or ZY1 to avoid confusion with ground infantry or fixed wing markers. To allow the mortar team to quickly navigate to the relayed location, it is encouraged to additionally communicate the grid reference.

    Example:  “steel rain 1-1, this is rain maker. fire for effect. TARGET MARK SIERRA ONE, grid ZERO THREE FIVE ZERO THREE FOUR.”


    Shift from known position

    This is an ADVANCED method to relay target locations.

    Using this method is only advised when GPS systems are not in use during the mission or when the observer has no map available. This requires both the observer as the mortar team to have prior knowledge with this method. The observer will select easily identified points on the map (such as buildings, crossroads, …) and reference and communicate these locations beforehand. This way, the observer only needs to calculate the direction and distance from a known point to communicate target locations.

    Steps to undertake:

    1. Select a known point, example KNOWN POINT 1. (example: a distinguishable church on the outskirts of a city). This point must be known to both observer and the mortar team.
    2. Calculate the targets location in relationship to the known point. Ideally, you will specify a distance and cardinal direction (example: 100m North-West)


    “Steel Rain 1-1, this is Rain Maker. KNOWN POINT 1 is the lighthouse on the south east part of Chernogorsk, confirm, over.”

    “Rain maker this is Steel Rain 1-1, known point 1 is light house on south east part of Chernogorsk, confirmed, out.”


    Correcting fire missions using known point method

    When correcting fire missions using this method, you can send three type of corrections. These corrections require knowledge of the known point and the observer’s current position, as the calculations are based on the observer’s view point of the target.

    • Ranging shift: how much closer or far away the target is in relation to the known point.
    • Lateral shift: how much to the left or right in relation to the known point. Using cardinal direction is also possible.
    • Vertical shift: how much the target is above or below the known point (only required to calculate if there is a big difference between the two reference markers)

    Example:” steel rain 1-1, this is rain maker. fire for effect, SHIFT FROM KNOWN POINT “CHURCH”, EAST 200”

    Example 2: “steel rain 1-1, this is rain maker. fire for effect, SHIFT FROM KNOWN POINT “ATC”, LEFT 100, ADD 200”


    ADD: how much farther the target is compared to known point
    DROP: how much closer the target is compared to known point


    3. Method of fire

    Ammo count and type

    In every fire mission, the observer will select the correct ammunition and amount. Standard mortar teams have three types of ammunition:

    • HE rounds
    • Smoke rounds
    • Illumination

    When ordering a fire mission, the observer will call out the amount and type of ammunition.

    Example: “steel rain 1-1, this is rain maker. Fire for effect, grid 035 034, 3 TIMES HE.”


    When requesting a fire mission, the observer will always announce the method of fire after giving the ammo count and type.


    At my command

    If RTO wants to control the time of impact, he includes AT MY COMMAND in the transmission. When the mortar team is ready with calculating the target location and has rounds loaded, the loader will announce “HAMMER 1-1 is ready, over.”

    RTO will announce FIRE at his discretion. AT MY COMMAND stays in effect until the end of the fire mission, or when cancelled with “CANCEL AT MY COMMAND”.

    Example: “steel rain 1-1, this is rain maker. Fire for effect, grid 035 034, 1 times HE, AT MY COMMAND.”


    Fire when ready

    The mortar team will deploy mortar rounds as soon as they are able to. The fire mission will end as soon as the mortar team has deployed the amount of rounds requested by RTO.

    Example: “steel rain 1-1, this is rain maker. Fire for effect, grid 035 034, 3 times smoke, FIRE WHEN READY.”


    Time on target

    RTO requests the mortar team to shell the target location at a specific time frame.

    Example: “TIME ON TARGET 5 minutes from now.”


    Continuous fire

    The mortar team will load and fire as fast as possible while maintaining accuracy, until RTO cancels the fire mission with command CEASE LOADING.


    If needed, the RTO will relay dispersion information when requesting more than one single round on a target location. The standard dispersion is 100m in a circular radius. The RTO can communicate different dispersion methods. If requesting a straight dispersion line, the RTO will communicate the amount of rounds, the initial starting position and the distance and cardinal direction of the other rounds.

    Example: “steel rain 1-1, this is rain maker. Fire for effect, grid 035 034, 3 times HE, fire when ready, DISPERSION 50M EAST.”


    Additional notes

    Danger close

    Danger close and position of friendlies will have to be communicated when ordering a fire mission if friendly troops are closer than 400m of the target location.

    Battle Damage assessment

    If applicable, a BDA is advised after each fire mission. The report will cover the effectiveness of the fire mission.


    Map Tools



    Range Table

    Vector 21

    (Micro)DAGR: the DAGR can be used to link your Vector 21 to your DAGR, allowing you to calculate 10 digit grids.



    Edited by Chuck Yeager

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