One of the most fascinating aspects to newcomers to the Squad Leader/Cross of Iron system, and one which can be really perplexing, is the really chaotic nature of the AFV "kill" system.

In my previous article on Squad Leader, an analysis of the system showed that even at point blank range a kill would usually occur less than 57% of the times a shell hit an AFV, and many players "fondly" remember the day their Mark IV on Hill 621 was hit eight times by T34s and survived to save the day (Russian players may not view the situation so memorably, however).

Cross of Iron continues the tradition, and a review of the hit/kill relationships has disclosed a range of 17-72% kill probabilities for most of the more common tank-vs.-tank matchups. As has been pointed out before, in my article on the COI armor rules, the system's low kill percentages stem in part from the fact that despite a gun being able to "theoretically" penetrate the frontal armor of the target (Tiger "88" vs. T34 at 320 meters), the probability of destroying the vehicle hit is not necessarily 100%, and is in fact usually quite low compared to our preconceived notions.

After suffering through the heartwrenching wails and moans of gamers whose Mark IVhs 75mm high velocity shells bounced off a T34 like it was an ogre (perhaps the intentional immobilization rule in COI was "borrowed" from Ogre after early playtesting revealed the "invulnerability" of the tank armor), a few gamers started to compare the kill percentages of COI and other miniature rules.

Except for Stalk I, where the chance of a kill ranged from 33% to 100%. depending upon how much more armor the shell could penetrate as compared to what it hit, if a shell could penetrate the armor it struck, in most rules a "brew up" or at least substantial damage was sure to follow.

Using the sources available, a chart and graph were prepared that compared the ratio of the gun's penetrating capability (AP) at 500 meters (12 hexes in COI) to the frontal armor of the target. These ratios ran from just under 1.0 to over 5.0, and were then plotted against the AFV kill probabilities for the gun/target case from COI.

The result of the graphic analysis were very interesting insofar as they confirmed our suspicions that significant AP/armor ratios were required to attain a high probability of a kill after a hit. For a ratio of 1.0, which in most games buys one a burned out or abandoned AFV (AP equals armor, or a "marginal penetration"), the COI "doomsday" percentages ranged from 3% (for the 37L) to 57% (for the monstrous 100L).

What is really surprising is that even when the AP value is twice the armor thickness ("double kill"), the Panther's super high velocity gun only "downs its prey" 67% of the strikes, with the gnat-like 37L cashing in on 28% of the hits.

Translated into game realities, the results can be rather traumatic as 37L shells smash into halftracks and fail to stop the vehicle 57% of the time despite the armor being only slightly more than a Datsun has. What other rules come up with something like this, and how does one explain it?

As far as explaining the apparent anomaly goes, it appears that one or two central issues are critical to the understanding of the results, and they concern the problems of internal damage and angle of incidence of the striking shell.

Theoretical armor piercing data is based on a fairly new gun and armor plate that is hit "head on" in most cases. Under actual combat conditions, the barrel may be partially worn, the shells may contain different powder charges, and the weather may be adverse to the performance of the weapon. In addition, the shell might hit armor at both a vertical and horizontal angle which increases the effective thickness of the plate the shell has to bore through, not to mention spare tracks, wheels and other equipment covering the surface.

While one may argue that previously hit armor might be weaker, the chance of hitting a vehicle perpendicular to the armor is rather slim and the odds for the shot tumbling or bouncing/skidding against the angled plate are rather good (hitting a plate at 30 degree from perpendicular increases the theoretical effective thickness by 20%).

The ability to overcome all of the miscellaneous little hindrances to piercing armor plate (angle of incidence, spare tracks, etc.) should increase as the theoretical AP value goes up, and the graph depicts this fact although "sure kills" are reserved for Tiger IIs against armored cars and other interesting and subtle matchups.

The second factor, and one which is often overlooked, is the lethality of the shell in terms of its ability to "undo" the inner workings of the target.

For instance, a 20mm shell that hits the armor of a halftrack may be able to penetrate twice the plate thickness it hit, but twice 10mm is still next to nothing. After getting through the body of the vehicle, the energy left might be insufficient to do any further damage unless it caught the driver's arm or leg. In comparison, the "88" shell that can penetrate twice the armor it hit will still have enough momentum remaining to wreak havoc inside the vehicle (German shells were designed to explode after penetrating, and an 88mm shell is sure to be more noticeable than a 20mm 'shotgun load' once it does "its thing'').

Killing ability should therefore be both a function of shell diameter ("battering ram" effect) and AP-to-armor ratio (a measure of excess energy after penetration), and here again Cross of Iron has provided for both factors in the AFV kill table.

Target	Frontal Armor	Firing Weapon	500 meters Armor Penetration	500 meter Kill Probability
BT7 BT7 BT7 T34/76 T34/76 T34/76 T34/76 BT7 JS II JS II JS II Tiger I Panther King Tiger Mark IVh Pz38t Halftrack STG IIIb Mark IVh Halftrack	22mm 22mm 22mm 75mm 75mm 75mm 75mm 22mm 120mm 120mm 120mm 100mm 120-160mm 190mm+ 50-80mm 25mm 10mm 50mm 50-80mm 10mm	75L 50 50L 75L 50L 88L 75LL 37L 75L 88L 75LL 100L 100L 100L 45L 45L 50/45L 45L 100L 37L	110mm 50mm 75mm 110mm 75mm 150mm 170mm 45mm 110mm 150mm 170mm 190mm 190mm 190mm 50mm 50mm 50mm 50mm 190mm 45mm	83% 57% 72% 48% 17% 57% 72% 28% 28% 43% 57% 83% 72% 57% 8% 43% 72% 17% 92% 43%
Source:	Cross of Iron AFV Kill Table Stalk I Miniature Rules German Tanks of WWII, Etterlin & Von Senger Tractics

Sensitivity of COI Kill Probabilities to AP/Armor Ratio

If one looks in the graph once again, and sights up the AP/Armor ratio of 1.0 line, the kill probabilities are in order of shell diameter and relative barrel length, which is exactly what one would expect after the previous discussion. Against "once penetrated" armor, the larger the shell the better the chance of . success.

While there are a number of strange data points on the graph (75LL vs. 88L, and 50 vs. 75L), it is possible that they are due to irregularities in the data used to make the plot, since the greater majority of the points follow the trend previously identified.

Based on the analysis of the COI data, it appears that the system is not as wild and unreasonable as most players might suspect, and that the game introduces the significant factors that affect tank kills in an intuitive and general way that is in line with COI's dedication to playable mechanics (at least for AFV kills, at any rate).

While many players might still find some of the combat results and gun ratings unfathomable, overall the COI system appears to have taken on the overly complex problem of coordinating the almost infinite different conditions that may exist when a shell hits armor and related them to just two or three numbers (armor DRMs and gun "kill numbers"). It may not be perfect or pleasant (especially if one prefers Tigers with "automatic kill" abilities), but looking at the whole picture it's both playable and comprehensive.

As a final comment of sorts, it should be noted that to date very little in the way of actual battlefield reports has been used to either verify or substantiate the assumptions made in war games on tank gun effectiveness. While in Tobruk 50% of all "88" hits on Stuarts "bounce away," the WRG rules insist that all hits will utterly annihilate the light tank, and Cross of Iron is somewhere in between (17% of the hits "do no evil").

With such a wide range of results and assumptions, it's no wonder that as one goes from game to game, many wargamers suffer from a sort of "jet lag" disorientation and bewilderment.

While part of the problem can no doubt be ascribed to different allowable rates of fire, varying mechanics and terrain considerations (wide open venue closed-in countryside), it would be nice to know that what happens on the game board or miniature table at least is mildly consistent with actual experience and reports, and is not based entirely on some gamechair designers' theoretical musings and/or the "experience" of what they saw while watching "Combat" on TV.

Brazen Chariots: A Review of the CROSS OF IRON Armor Rules, Part 1
Brazen Chariots: A Review of the CROSS OF IRON Armor Rules, Part 2