The Operational Art of War

Designer's Notes#1

* How are unit movement allowances calculated?
* Why doesn’t enemy controlled territory block lines of communication for supply purposes?
* How were weapon characteristics determined?
* What is an infantry squad? Which should I use for my scenarios?
* Why are units represented in so much detail? Why isn’t there a simple table of terrain effects on unit combat strengths?
* Why are the strengths shown in the quick reference displays (unit icon, information panel) different from the detailed strengths used to resolve combats, and what relationship do the displayed numbers have to the actual unit strengths?
* Why can air and (to a lesser extent) artillery units participate in so many combats during a turn?
* What is evaporation?
* What significant changes have been made to the simulation elements of the game since version 1.00? Why have they been made?


How are unit movement allowances calculated?

Unit movement is based on scenario scale and the mix of equipment assigned. Most equipment movement capabilities come in the following flavors:

Naval move

4200 km per week

Fast motorized move

660 km per week

Motorized move

560 km per week

Slow motorized move

350 km per week

Horse move

400 km per week

Foot move

280 km per week

These nominal (and optimistic) movement figures are based on actual figures for large formations over the period 1850-1944. The horse movement figure is actually a bit high according to real world records, but use of real world movement rates resulted in cavalry units being slower than light infantry in the game (which while true, according to historical records, was offensive to most wargamers accustomed to "cavalry moves faster" movement rates in most wargames to date.)

Now things start getting strange...

Late in development I realized that some folks really wanted to mix strange scales. Don't ask why. I didn't. But the problem was that at the ends of the scales unit movement based on "real" figures resulted in "bad" movement allowances. So I imposed a constraint function over the movement calculation algorithm to speed things up at the low end and slow things down at the high end. This code takes a look at the highest possible nominal mechanized movement rate and generates a constant ranging from 0.22 (if the highest raw allowance is greater than 200) to 8.0 (if the highest raw movement allowance is less than or equal to 1) - with little or no modification for values between 11 and 30, which should be typical for scenarios using balanced scales. This constant is applied to all raw unit movement rates in a scenario to create those actually used.

There was also the question of units composed of dissimilar equipment. Originally, I based the movement allowances on the slowest equipment in the unit (using transport to speed it up if available). There were folks who didn't like this, so the code was changed to reflect the mean movement characteristics of the equipment - which means unit movement in the game actually models the mean location of the unit. In some cases, the unit would actually be spread over several hexes by the end of a maximum move - but the result met with the approval of the test group, and one can argue that this model is as valid as a "slowest" equipment determination.

Those with training in physics might find this amusing: the precision of a unit's location is inversely proportional to the known speed at which the unit moves to get there.

Why doesn’t enemy controlled territory block lines of communication for supply purposes?

What is "enemy controlled territory"? In TOAW it is a location that was last occupied by the other fellow. Unless you put something in or adjacent to a location nothing is assumed to be there to stop the trucks, mules, bearers, etc. Empty locations are not assumed to be chock full of steely eyed military police. Why should it be any other way? If you keep in mind the fact that units block supply passage in and adjacent to their location, it isn’t difficult at all to isolate large pockets of enemy units once you break through his defenses.

How were weapon characteristics determined?

All weapon characteristics are intended to reflect the general utility of the weapon in the operational scale. Lethality is based on the amount of metal and explosives the weapon can throw down range. In the case of anti-tank weapons, the ability to hit and penetrate armor is also considered. Finally, all figures are multiplied by a constant to help avoid overflow errors in game calculations and make the numbers easier for players to read.

The lethality of a long range indirect fire artillery piece, for example, is based on the size of the round. Lethality per round is equal to the square root of half the caliber of the round (in millimeters) cubed. L=(c/2)^(3/2). Why? The amount of explosive in the round is based on the volume of the round, thus the cube. But the damage done by an explosive round falls off with the square of the distance from the point of impact. So a 150mm round is not simply twice as nasty as a 75mm round. It is almost 3 times as lethal. But lethality per round does not tell the whole story. If you look at the figures for these two weapons in the manual you will see that the 150mm gun is only about twice as lethal as the 75mm gun. Why? The 75mm weapon has a higher rate of fire. Indirect fire artillery lethalities are modified by a function intended to represent the effect of rate of fire on overall lethality.

Anti-tank weapons are even more complicated. Due to their nature, they are also subject to debate. The available references tend to disagree on characteristics, particularly for obscure weapons. Lethality per round is based on the sum of the round’s ability to penetrate multiplied by its ability to hit, determined at 250 meter increments out to 2km. This is a discrete integration or "area under the curve" calculation. Thus an inaccurate long range weapon with moderate penetration capability might have game characteristics similar to a more accurate short range weapon with very high penetration capabilities. Even more than with indirect fire artillery, rate of fire is a critical modifier for anti-tank weapons. This is why some of the big anti-tank guns developed toward the end of WWII actually have lower game anti-armor strengths than many smaller weapons. A 100mm AT gun may well be able to destroy anything on the battlefield with a single shot, but that is small consolation if the other guy hits you three times with smaller (but still nasty) chunks of metal while you’re trying to get round number two off. Adding to the complication is the question of special ammunition. While just about all WWII belligerents developed special ammunition that dramatically improved the performance of existing weapons, some countries were not able or willing to pay the costs of actually supplying the special ammunition to troops in the field. The Soviets, for example, just didn’t seem to care very much. And the Germans didn’t have access to sufficient quantities of the necessary exotic metals.

Finally, many folks seem to forget that most tanks carry machine guns. Even a medium machine gun has a limited anti armor capability. Under certain circumstances, heavy machine guns (12.7mm or larger) can be dangerous even to many medium tanks in this period. Then there is the anti-personnel strength effect of vehicle mounted machine guns. For many of the tanks represented in TOAW the machine guns’ contribution to the vehicle’s anti-armor and anti-personnel strengths is substantial.

What is an infantry squad? Which should I use for my scenarios?

Infantry squads in TOAW are intended to represent standard units of about 10 soldiers with their personal weapons and any heavy weapons normally assigned at squad level. For many rifle squads in the game this includes one or more attached light machine guns. It does not include weapons sometimes attached at the platoon level, including light mortars or medium machine guns. The "correct" type of squad for any particular type of unit varies with nationality and time period. Here are a few examples:

A platoon would typically have two to four rifle squads as well as a number of platoon level heavy weapons (light mortars and light or medium machine guns).

Why are units represented in so much detail? Why isn’t there a simple table of terrain effects on unit combat strengths?

Part of the reason is historical "chrome". Many players like to know what kinds of weapons their units are armed with. But there are important simulation (realism) reasons as well. Real world military units are organized collections of troops and equipment. Except in the simplest cases, they are not well modeled as black boxes with arbitrary "attack" and "defense" strengths. Different types of equipment have different tasks and are exposed to different hazards under enemy fire.

Take the simple case of an infantry regiment under attack. If the unit is in a prepared position, (defending, entrenched, or fortified) the different types of equipment assigned to the unit benefit to greater or lesser extent depending upon specific characteristics. Infantry gains tremendous benefits from prepared positions. Artillery gains smaller benefits, and vehicles get the smallest benefit of all. The overall effect of the prepared position depends upon the exact mix of equipment in the unit. When the enemy attacks, all of the different strength and capability modifiers are taken into account to determine the actual performance of the unit. Then there is the "structure" of a battle to consider. Artillery fires first, followed by anti-personnel and anti-armor fire. It is possible for units to retreat or break off after just the artillery fire. Unless the unit is very small, or under attack from the rear or flank, things like trucks and guns are much less subject to losses than infantry and tanks. So if a badly mauled infantry regiment retreats from combat, its line troops may be decimated while the support elements (artillery, transport) are hardly damaged. And this barely scratches the surface of what we can do using equipment based units. How could you simulate these effects with monolithic (not equipment based) units? You can’t. Now the detail doesn’t have to be rubbed in players’ faces. In fact, you can play TOAW without ever looking at the details in a unit report. But since the details are necessary for simulation reasons, I decided there was no great harm in making them available for curious players as well.

Finally, believe it or not, building units up from a database of available equipment makes it easier for scenario designers to do a good job of creating units with historical capabilities. As long as they have access to order of battle and unit proficiency information they can simply build the units from their references. Assuming no significant problems with the equipment database, these units will have historical capabilities.

Why are the strengths shown in the quick reference displays (unit icon, information panel) different from the detailed strengths used to resolve combats, and what relationship do the displayed numbers have to the actual unit strengths?

The strengths shown in some of the game displays are scaled to two digits. This is done to allow us to show useful information to players. Contrary to what some of our mathematically challenged brethren seem to think, the scaled reference numbers are directly related to unit performance. Scaling the numbers does not invalidate them. It merely allows us to show them in the space available. Because of the way the scaling works, very small units don’t differentiate all that well. One unit with a displayed strength of 1 might actually be almost twice as strong as another unit with a displayed strength of 1. But in most scenarios, these small units are both rare and fragile. Load a scenario and check it out. A battle between two such "1 strength" units is relatively unpredictable, in part because both units are typically on the verge of evaporation. That’s not such a bad thing. But a unit with a displayed strength of 3 really is about three times as strong as a unit with a displayed strength of 1. Given the uncertainties of combat, the knowledge that the actual internal strengths are 103,100 vs. 37,500 would be useless to players.

Why can air and (to a lesser extent) artillery units participate in so many combats during a turn?

Given the time scale of a typical scenario, most air units and artillery batteries dedicated to battlefield support spend much of their time waiting for specific orders. They are capable of Herculean "surge" capabilities when the requests begin to flow in, although at the expense of significant readiness and supply costs. Air and fire missions are simply added to the queue and somehow manage to get done right up to the point that the unit runs out of aircraft or artillery tubes – typically well beyond the nominal capability of the unit. This is one subject I know from first hand experience (USAF 1976-1980). Few things are more depressing to an avionics weenie (me) in an interceptor squadron than the sight of 16 "broken" airplanes after a surge. To borrow a game analogy – it’s orange stripe time.

What is evaporation?

Evaporation happens whenever a unit loses cohesion. While history is replete with tales of units that fought to the last man, these are unusual cases. There are many more examples of units that simply dissolved, even if only temporarily, under enemy fire. Units, even good units, can only take so much.

In most cases evaporation is different from what most wargamers are used to calling "elimination". Unless the evaporating unit is isolated, all surviving troops and equipment are still available for distribution to other units. Isolated units (those not able to trace a line of communication back to a friendly supply point), on the other hand, are truly eliminated when they evaporate. Their troops and equipment are permanently lost – assumed surrendered to enemy forces.

Time allowing, many evaporated units will eventually be reconstituted from available replacements.

What significant changes have been made to the simulation elements of the game since version 1.00? Why have they been made?

I originally intended that changes to unit deployments, including digging and reserve deployments, could only be made if a unit had not moved previously in the turn. Then late in development the right mouse button context menu for giving unit orders was added. The code checking for menu ordered deployment changes was slightly different from that used in the unit report, and allowed deployment changes for previously moved units. We all got used to using the right mouse button menu to issue unit orders and the original restrictions were forgotten. During the preparation of the 1.01 update I removed the extra check from the menu construction code and substituted the original more restrictive code. Turns out nobody, including myself, really liked the original code after having more flexible rules – so it was relaxed again with v1.02.

Disengagement is now treated in greater detail. There were things that were not being considered in the original code – such at terrain, time of day, and weather conditions. Some folks still prefer to be able to avoid disengagement altogether, so I also gave players the option to disable it completely in v1.02.

Supply lines are now determined very differently from versions prior to 1.03. All supplies are now distributed through a "fully supplied" net that can only spread out from supply points over contiguous friendly controlled road, railroad, anchorage, airfield, urban and open locations. Only units on the fully supplied net draw the maximum available supplies. Units able to trace a line of communications no more than 4 locations long to any point on the fully supplied net now draw 2/3 supplies. All other units capable of tracing a line of communications of any length to a friendly supply point draw 1/3 supplies. In most cases this gives very similar results to the original system for units on or behind friendly lines. But it does dramatically cut the ability to re-supply units bypassed by enemy advances.

Originally, armor heavy forces had a tendency to break off attacks against defending forces with strong anti-tank capabilities before they had a chance to inflict casualties on the defenders. This meant pure armor or armor heavy units operating without infantry and artillery support had a tendency to bounce without doing much damage. I changed the combat resolution slightly so that armor and anti-armor fire are now resolved simultaneously. Pure armor still has a tendency to bounce from attacks on positions with strong anti-tank capabilities, but it now inflicts considerable damage on the defenders in the process.

Updated July 30th, 1998.


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