the_iron_duke
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I was interested in finding some real world data about military force ratio - that is, the effect that an attacker's (numerical) superiority over a defender has on the probability of a successful attack.
Here is a brief summary of the concept of force ratio:
quote:
Until now, historical ratios, exemplified by the 3:1 ratio of forces required for a successful attack, have been treated as fact. In accordance with conventional practice, a friendly force that achieves the established ratio guidelines is able to execute its wartime tasks: 3:1 to attack a prepared position; 2.5:1 to conduct a hasty attack; 1:1 counterattack; 1:2.5 execute a hasty defense; 1:3 defend from prepared position; and 1:6 delay. These rules of thumb are important because they establish a statistical baseline for successful operations. Essentially, if a force achieves a historical force ratio, then the U.S. Army states that it historically has a 50% chance of success [my emphasis]. -Combat Power Analysis is Combat Power Density - Major James A. Zanella, United States Army
These ratios are built on the assumption that the attacker's and defender's forces have the same combat strength, an abstracted value that would include things like personnel strength, training, equipment, morale, readiness, cohesion and so on. So it's a hypothetical guide and easier to replicate in a wargame, since one can create units with the attacker and defender having identical attributes.
I also found in another thread on another forum a link to the following chart, which was described as originating from the Defence Science and Technology Lab, an agency sponsored by the United Kingdom's Ministry of Defence. While the article that the chart derives from is not available, its figures correlate with the force ratios described above from the other source, so I believe it has some usefulness.
From the chart, we can extrapolate the following set of figures. These are the force ratios required for an attacker to have an even odds, 50/50 fight against a defender:
Meeting Engagement: 1/1
Hasty Attack vs Hasty Defence: 2.5/1
Hasty Attack vs Prepared Defence: 3.75/1
Hasty Attack vs Breaching: 5.3/1
Prepared Attack vs Hasty Defence: 2/1
Prepared Attack vs Prepared Defence: 3/1
Prepared Attack vs Breaching: 4/1
Here are some descriptions of the listed situations, along with my analysis of how they should be treated for wargame purposes.
Meeting Engagement
quote:
In warfare, a meeting engagement, or encounter battle, is a combat action that occurs when a moving force, incompletely deployed for battle, engages an enemy at an unexpected time and place.
Since odds are even, I think we can assume that this would represent an attacker and defender fighting with no other combat modifiers.
Hasty Attack
quote:
In land operations, an attack in which preparation time is traded for speed in order to exploit an opportunity.
I think this would represent an attack where an attacker attacks a defending enemy unit without the attack being first prepared by supporting units, notably through artillery or air bombardment. So it would represent an attacker attacking an unsuppressed enemy.
Prepared Attack
quote:
A type of offensive action characterized by preplanned coordinated employment of firepower and maneuver to close with and destroy or capture the enemy. [Definition is of "deliberate attack", which I believe to be synonymous with "prepared attack"]
So I think this would represent an attack where artillery or air bombardment has been taken place prior to the attack and the enemy has therefore been fully suppressed by suppressive fire.
Let's quickly discuss what exactly we mean by suppressive fire. Here is the NATO definition: "fire that degrades the performance of an enemy force below the level needed to fulfill its mission. Suppression is usually only effective for the duration of the fire". From wikipedia: "The purpose of suppression is to stop or prevent the enemy from observing, shooting, moving or carrying out other military tasks that interfere (or could interfere) with the activities of friendly forces. An important feature of suppressive fire is that it is only effective while it lasts and that it has sufficient intensity...Colloquially, this goal is expressed as 'it makes them keep their heads down' or 'it keeps them pinned down'".
So suppressive fire represents just one specific effect of (artillery) bombardment and its effects are also short-lived - in game terms, the effects of suppression should have a duration of only one turn.
From the chart, we can also determine the value of suppressive fire. Here are the force ratios for the different attacking situations.
Attacking Hasty Defense: (Hasty Attack/Prepared Attack) 2.5:1 vs 2:1 = difference of -20%
Attacking Prepared Defense: 3.75:1 vs 3:1 = difference of -20%
Attacking Breaching: 5.3 vs 4:1 = difference of -25%
So it can be determined that the value of suppressive fire is that it reduces the defender's combat effectiveness by 20-25%. Of course, any artillery bombardment undertaken to raise an enemy unit's suppression level to 100%, would also be inflicting other damage to it (and its hex, potentially). A fuller list of the effects of bombardment would include:
1) Killing enemy. It's reported that the majority of casualties in the Second World war came from bombardment of one kind of another. This probably, in addition to artillery, would include air bombardment and mortars (the latter of which are often modelled in game terms as infantry units, rather than artillery). Here's a reported set of figures of British Second World War casualties and their causes:
Mortar, grenade, bomb, shell ...........75%
Bullet, AT mine................................10%
mine & booby trap...........................10%
Blast and crush.................................2%
Chemical..........................................2%
other................................................1%
2) Suppression of enemy - fully suppressed enemy is 20-25% weaker for ONE turn
3) Reducing defenders' unit entrenchment - reduces the entrenchment that a unit builds up automatically over a few turns by staying in the same hex
4) Reducing defender's unit morale/cohesion/readiness. Artillery should do some slow general attrition to these attributes.
5) Damaging fortifications - if prepared fortifications have hit points.
Therefore, in game terms, I would understand the difference between a Hasty Attack and Prepared Attack to be that the combat strengths of the attacker and defender are identical and the only difference would be that in a Hasty Attack the defender is 0% suppressed, while a Prepared Attack would mean that the defender had been 100% suppressed.
Just to reiterate, suppression is not analogous to shellshocking the enemy - a unit could potentially have 100% readiness/morale and be 100% suppressed and vice versa. Breaking a defender's spirit through artillery bombardment would be done through degrading its readiness/morale, rather than through the effect of suppressive fire.
As a side note, I feel the suppressive fire value of small arms, such as infantry MGs, is also simulated in game terms through hex Zone of Control rules, such as an attacker having its movement end, or its movement points reduced, when entering hexes adjacent to enemy units.
Hasty Defense
quote:
A defense normally organized while in contact with the enemy or when contact is imminent and time available for the organization is limited. It is characterized by improvement of the natural defensive strength of the terrain by utilization of foxholes, emplacements, and obstacles.
I think that this should represent the automatic entrenchment that a unit builds up when not moving from a hex for a few turns. So this value on the chart would represent a unit that had been stationary for a while and had achieved 100% of its unit entrenchment bonus.
Prepared Defense
quote:
A defense normally organized when out of contact with the enemy or when contact with the enemy is not imminent and time for organization is available. It normally includes an extensive fortified zone incorporating pillboxes, forts, and communications systems. See also hasty defense.
I think this would represent fortifications that had been constructed on the battlefield, thereby changing a hex's base defensive modifiers. This could be fortifications that the player has built on the map (using engineers) or, in other games, terrain hexes might have been already pre-placed on the map as fortifications tiles.
Breaching
Without the accompanying text, it's not clear exactly what "breaching" refers to in this instance. It could refer to general obstacle breaching:
quote:
Breaching operations are conducted to allow maneuver despite the presence of obstacles. Obstacle breaching is the employment of a combination of tactics and techniques to advance an attacking force to the
far side of an obstacle that is covered by fire. It is perhaps the single, most difficult combat task a force can encounter...e. An obstacle is any obstruction that is designed or employed to disrupt, fix, turn, or block the movement of an opposing force (OPFOR) and to impose additional losses in personnel, time, and equipment on the OPFOR... Obstacles can exist naturally (existing), be man-made (reinforcing), or be a combination of both.
So it sounds a pretty general term that could encompass any difficult terrain hex that is defended by the enemy, like a city or hill. It could also potentially refer to door breaching - forcing closed or locked doors - and so be being used in this instance to refer to house-to-house clearance of urban areas. Either way, I think we can presume that in game terms, "breaching" would correlate with the upper limit of defensive terrain hexes, so tiles like fort or urban areas.
Here's a summary then of the force ratio combat modifiers as I see it, adapted for wargame use:
Conclusions
So there are a few maxims that we can take from this force ratio analysis:
- A defender that has been stationary in one hex for a few turns and has achieved 100% unit entrenchment, will have an extra defensive combat strength bonus of +150% (so 250% of base combat strength).
- A prepared defence hex increases a unit's defensive bonus by +125% (so 225% of base combat strength). This is separate from a unit's own entrenchment modifier bonus.
- A hex of maximum defensive combat modifiers (e.g. fort, urban) gives a bonus of 280%. This is separate from a unit's own entrenchment modifier's bonus.
- Suppressive fire, which lasts for one turn, can reduce a defending enemy unit's combat effectiveness by 20% or, in the case of maximum defensive terrain hexes, by 25% (as per the chart). This is separate from other damage that the suppressive bombardment may do to the enemy unit (e.g. personnel casualties, unit entrenchment loss, readiness loss, fortification damage).
Example
Let us go through an example: a defender has been in a maximum defensive combat modifier hex, such as a city perhaps, for a number of turns and has achieved 100% of its own unit entrenchment bonus.
- a unit fully entrenched using its own unit entrenchment gives a bonus of +150%
- a max defense/"breaching" hex gives a bonus of +280%
So the defending unit's combat bonus would be (150 + 280) = +430% (so 530% of unit's original strength). Therefore the force ratio for attacking the enemy, in this instance, and getting an even odds 50/50 battle would be 5.3:1.
These would be the odds for performing a Hasty Attack, at least. The odds would be reduced by performing a Prepared Attack, i.e. making the enemy 100% supressed through artillery or air bombardment. In the other attacking circumstances, this would reduce the enemy's combat effectiveness by 20%, but against the max defensive/breaching hex, this would be 25% (as per the chart above).
Of course, in reality, bombardment of the enemy in order to suppress it would also be doing other damage to it (e.g. personnel casualties, unit entrenchment loss, readiness loss, hex fortification damage), but if hypothetically the only damage the attacking bombardment did to the enemy was suppression damage (to maximum suppression), then it would be a 25% combat effectiveness reduction.
So 530% (100 + 430%) - 25% = 400%
The defender's combat effectiveness would thus be reduced from a +430% bonus to a +300% bonus and the force ratio required for an even odds attack reduced from 5.3:1 to 4:1.
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Force Ratio: Analysis and Application in Wargames - 
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