FORCES Direct Combat Ground Fighting Algorithm

This document addresses the current JFORCES direct ground fighting algorithm. It does not incorporate discussion of air-ground, ground-air, artillery, minefield or other similar attacks involving ground units. These will be described in other sections.

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Overview:

Ground engagements begin either when directed by exercise players or when otherwise unengaged units approach each other. The range at which automated engagement becomes an option and the cycle at which the the simulation checks for these engagements is user defined during Mission Planning under the "Scenario Defn->Scenario Configuration->Ground Fighting Parameters" option. The units involved in the engagement stop moving according to route directives (either preplanned or issued by a commander-in-the-loop) during the engagement but will resume their directed movement after the engagement is complete. Not all subunits of a unit involved in an engagement are automatically automatically involved in the same engagement. Those subunits determined to be too far from the engagement center are not automatically incorporated into the engagement and thus can continue to maneuver and perform missions independently. For example, a reserve company would not automatically be included in an engagement when the rest of the battalion is engaged, so it can operate independently. However, this also means that the user would have to direct the movement of this company to support the attack when it's desired to reinforce the rest of the battleon.

Combat losses are calculated on a periodic basis by the current JFORCES direct ground combat algorthm. Thus, if the update cycle is set to 5 minutes in the Mission Planner, every 5 minutes the losses are updated for each sides. Losses would not occur due to this engagement between these updates, though losses from other sources (including air strikes, artillery attacks and other ground engagements) might reduce either of these combatants between the cyclical updates and these can dramatically effect the outcome of subsequent loss calculations. Basically, weakening one side through supporting attacks will leverage direct combat success.

The current FORCES direct ground combat algorthm models ground fighting between ground units in close proximity. Losses and kills are computed periodically by a modified Lanchester approach that aggregates combatants into engagement subgroups based upon their side and range from the engagement center. The firepower of each subgroup is determined by the type(s) of assets in that subgroup and the range band. This firepower is then modified according to the team logistics, the overall friendly force detection success against the engaged enemies, training and other factors enumerated below. Based upon the summation of each side's firepower across all range bands an estimate is made for the expected number of kills versus a typical unprotected enemy. This expeccted number of kills is then converted to a raw PK versus each enemy by dividing it evenly across all enemies "close" to the engagement front line. The participants close to the front line are considered targets for the enemy. Their actual losses are based upon this initial raw PK as modified for each target according to scenario factors including the geometry from the engagement center to the participant (to determine front/flank/rear attacks), posture (e.g. Dug in), morale, and target armor.

As described above, engaged units stop their maneuvers when engaged in ground fighting. Instead they either advance or retreat from the enemy in accordance with their success, mission orders and combat role. This will allow winning main battle tanks to advance, support units to attempt to maintain separation, and loosing units to retreat. Engagements end when units separate outside close combat range.

Determination of New Engagements

New engagements are created either by user direction or by automated rule. Users can direct engagements either interactively or prescript them using the Mission Planner. During runtime the interfaces to create an engagement can be found under "Scenario Controls->Ground Force Controls->Engagement". Either the "Area Ground Engagement" or "Specific Attacker Ground Engagement" option will generate a ground combat; it just depends how detailed the user wants the engagement command to be. The interface for prescripting ground engagements is found in the Mission Planner under "Scenario Defn->Specific Elements->Groups". Pick one of the units that should engage and go to "Position & Tasks". Then select "Check Operational Tasks". Click on "Add Task" and select "Prescripted Close Combat" from the presented list. Then fill in the menu and save. Note that in either case the engagement will be directed, but might be canceled immediately. This is common when the attacker and defender are far apart; they will not close on each other until in engagement. Maneuvering to closure is a user responsibility in either the interactive case or prescripted case. Use route creation options either for the group during prescripting or through the "Route Builder" interface to cause the units to close. See the Combat Termination section below for information on why attacks might terminate immediately.

More commonly, ground engagements start automatically when enemy units come within range of each other. The grndengmentcreate in sim/engment/grndengmentcreate.F is called periodically to determine whether two units from opposite sides are close to each other ("close" is as defined by the user in the Mission Planner interface under "Scenario Defn->Scenario Configuration->Ground Fighting Parameters") and at least one of the units is not already engaged. If both are previously engaged, even if not with each other, no additional engagements will be created. The period for calling this routine is either 30 seconds or the minimum simulation clock interval as defined by the user in the Mission Planner interface under "Scenario Defn->Sceanrio Configuration->Timing and Control", whichever time is greater. This means that if the user sets the minimum time interval to a large value its possible for two ground units to fly past each other without noticing.

Typically the autoengagement option works so well that users define scenarios in terms of maneuvers only and let the engagements occur automatically as the forces close.

Determination of Subgroups Involved in Specific Engagements

Generally, when a unit is involved in a conflict all reporting subunits are also involved. Thus, if a battalion is incorporated in an engagement all companies and platoons thar are part of that battalion also engage at the same time. But this is restricted if the subgroup is more than a range based upon the parent unit level from the engagement center. The current values for the max radius are that used are :

1 mile if the principle engaged unit is a platoon and below

1.5 miles for companies

2 miles for battalions

2.5 miles for regiments

5 miles for all echelons above regiment.

The values and code are found in the startgrdengment_ and group_to_engagement routines, both found in sim/engment/grdengment.c


Detailed Determination of Combat Results

The current JFORCES direct combat engagement model is based upon periodic calls to a mass-attrition algorithm basd upon Lanchester equations. The call period is as defined by the user in the Mission Planner interface under "Scenario Defn->Scenario Controls->Timing & Controls". Key routines are:

The basic processing is:

Compute the situation. This includes

The algorithm them loops through each engagement. The following is done for each engagement:

  1. The engagement area and geometry is evaluated.

  1. The firepower is calculated for each side. This is done by aggregating the firepower of ground engagement armament subsystems on all participants into range bands. The computed firepower is computed in the coutguns routine as follows:

firepower = sum(firepower * num_arms * training * contamination_factor) summed across all participants

where

The value for each asset engaged natually varies according to the asset type. The sum is then distibuted according to range bands across the targets to define a typical default PK for this update.

  1. It's determined whether the engagement should continue. Currently engagements continue until no participants can effect each other based upon the calculations in step 2. This can happen either because one side has been eliminated or maneuvered out of range.

  2. The actual probability of loss per minute for each specific participant is then computed as follows:

PL = (1--pk) * comm_factor * morale * terrain_factor * opposing_accuracy * opposing_logistics / armorrating

Where

Losses are then determined on an individual basis by drawing a random number versus this probability of loss (as adjusted by the calling cycle) in a Monte Carlo approach.

Combat Maneuvering Algorithm

Attempted maneuvering during combat is restricted to holding a position or advancing towards or retreating from an enemy according to the following table:


Orders Combat Role


Direct Combat

Fire Support

Combat Support

Service Support

Hold

Hold until < 50%/morale of initial strength; then change to retreat orders

Hold until < 50%/morale of initial strength; then change to retreat orders

Hold until < 50%/morale of initial strength; then change to retreat orders

Sit tight< 50%/morale of initial strength; then change to retreat orders

Pursue

Move at 15 konts towards enemy position

Close to within 2 miles of enemy

Maintain range 8 miles from engagement center

Sit tight

Engage & Advance

Move to initial enemy position; hold at that position when taken. This will result in resuming any prior movement shoulld the enemy be destroyed or disengage.

Close to within 2 miles of initial enemy position; hold at that position when taken. This will result in resuming any prior movement shoulld the enemy be destroyed or disengage.

Maintain range 8 miles from engagement center

Sit tight

Retreat

Move 15 miles away from enemy.

Move 17 miles away from enemy.

Move 23 miles away from enemy.

Sit tight


Note that the phase used is "attempted Maneuvering". Faster units will overtake and overwhelm slower ones, making the planned separation impossible.

This is implemented in the grd_combat_maneuver routine in grdengment.c. The rules and parameters are expected to be made available for user tailoring during Mission Planning after the approach has been approved.

Combat Termination

Currently engagements continue until no participants can effect each other based upon the calculations in step 2. This can happen either because one side has been eliminated or maneuvered out of range. The code to check for this is in the groundengment_ routine in sim/engment/grdengment.c. The action is implemented in cancelgrdengment_, also in this file. This latter routine is also responsible for restarting the unit on it's original route,assuming it had another route when the engagement began.