Wargamers’ Corner: Cobra II

August 27, 2014–I’ve been asked several times now, in connection with  my book Normandy Crucible, about making available to gamers the modifications I made in the wargame Cobra for purposes of creating the “wargame laboratory” I used as part of the research for that book. Most recently that question was posed directly on this website by gamers William Barnett-Lewis and Sergeant Skip Franklin. As we pass the 70th anniversary date I wanted to post something about why I don’t feel comfortable doing that. But I’ll also describe my process–and alert gamers will be able to craft their own “house” versions of the modifications.

Fundamentally it’s a question of publication rights. When I worked on that book and I wanted to put together a lab apparatus, that was for my own research and the only question was a suitable vehicle. The Simulations Publications (SPI) game Cobra had the right qualifications: a suitable geographic scope, a good level of unit representation; and, at one map, a game that was not impossible to keep up and get out of the way so that it could be used in spurts on a long-term basis.

But as for publishing amendments to the game, I would not want to do that without reference to the rights holders, and that’s a more ambiguous situation. Brad Hessel is the designer of record, but the game had editions from SPI and TSR Hobbies both. Most of the SPI/TSR games’ rights today belong to Decision Games but some do not, having been covered by direct contract between the publishers and designers (for example, my games Monty’s D-Day, Warsaw Rising, and Kanev reverted after publication). The situation with Brad I don’t know about. I asked around a bit, but no one I know seems to have his current address so I was unable to clarify the rights situation.

Now, if a publisher comes to me and wants a new Normandy breakout & pursuit game, I’ll gladly incorporate the features I am about to discuss. But short of that you’ll have to bear with me.

OK. There were certain problems with the Hessel Cobra design. One was that the Falaise Pocket battle rarely occurred with the game since the German line simply disintegrated, the German armies were destroyed and the Allied pieces rushed for the map edge. There were several reasons for this:

(a) One was the time scale. The game had three-day turns. The historical period for the Falaise Pocket typically ran out before the game reached the “pocket” stage. Switching to two-day turns allowed the history more time to develop.

(b) Most important was the issue of the Combat Results Table (CRT). This was an odds ratio CRT–very common for that time–and required mathematical calculation of a strength ratio between attacker and defender. Not only is that very cumbersome, since the society has moved so far away from these kinds of routine math problems, but all the trouble didn’t seem to be worth it–the strength disparities between the two sides were such that the vast majority of combats were resolved on the top few columns of the CRT.

This also meant that the German player had very few possibilities for counterattack, because his forces were just too thin to generate decent odds.

A related issue was with terrain effects. The requirements of the Terrain Effects Chart (TEC) were typically to shift columns, inserting an element of asymmetry with the odds ratio calculation. I thought that gave the idea. Change the CRT to a differential calculation. Now the attacker simply compares his strength with the opponent and immediately derives the CRT column. The “0” differential occurs at 1-2. Columns increase to advantage (+1), then by 5s to +25, then to +50, +75, +85, and 99+. Below zero the splits are at disadvantage (-1), -5, and -10 or less. The CRT generates step losses for both sides. In keeping with the larger differentials at high levels of advantage I used more higher-level loss results (e.g. 1/3, __/4) on high columns.

The one mathematical calculation I required was for troops attacking across rivers, who are halved or reduced to one-third strength depending on whether the river is minor or major. In general I converted most game effects to column shifts in keeping with this procedure. (For example, instead of doubling a stack (division), in this game unit integrity conveys a column-shift advantage.)

(c) Players might want to experiment with ZOC rules, giving Allied units and German mobile forces (because all are motorized) ZOCs but none to German infantry. That opened the game up when I used it.

(d) At the time of the original game the existence of intelligence (ULTRA) was just becoming known, much less understood in any detail. A major element was to insert intelligence rules. I added both sigint and combat intelligence (interrogation of prisoners). The former depended on an ULTRA table on which the players rolled each turn. That allowed the player to neutralize the divisional integrity of a certain number of opposing stacks and pre-emptively exhaust the column shift advantage of a number of Headquarters. (I also added Allied HQs for Bradley and Monty in addition to Patton). With combat intelligence, for every three losses the previous turn the player could neutralize the integrity of an opposing division.


Some German capabilities (Tiger Battalions, Nebelwerfer Brigades) were never modeled in the game. I added counters for these and endowed them with column-shift capabilities.

On the Allied side the rules governing the “Cobra” air strike were both too restrictive and too loose–too restrictive because they did not permit the Allies to create an actual break in the lines by means of a saturation attack, and too loose in that the player could stage a “Cobra”-level air mission every turn if he wanted to. (The Allies actually managed two “Cobra” equivalents plus two attacks that were of the same type but smaller.) I inserted a radically different rule on air strike effects that widened the sector struck and had target units incur losses, temporarily disappear, and reappear afterwards next to a friendly headquarters. This afforded the opportunity to open an actual hole.

At the time this game appeared in the 1970s, our knowledge of the Allied order of arrival, funneling fresh combat divisions into Normandy, was well developed, but our knowledge of the German side was much less perfect. So I created a new German order of appearance with units (and even replacements) arriving according to the historical record.

Apart from anything else I think these changes resulted in greatly improved historicity in this game. You can try it at home.


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