Interpenetration Optional Rule Clarification
In the new 4th Edition, the way interpenetration is handled at Napoleon's Battles has been heavily changed. After reviewing calculations about the footprint of the units and historical accounts, we judged that the way the previous editions treated this issue was not historically accurate enough, although it was very straightforward and very simple to handle.
With the new rule that has been included in the 4th Edition (Sect. 4.2 - page 37) the movement of Napoleon's Battles units passing through other units has been drastically reduced, and this changes the substantially the grand tactics and placement of the supporting units. As the current designers of the game, we feel comfortable with that. Certainly, the rule does not cover every incident that happened on the Napoleonic battlefield, but, as every other rule at the scale of this game, an approximation to the average facts must be done in order to preserve the flow of the game. More sophisticated rules were tested, but finally we decided that the rule that appears in the rulebook is a good compromise between historical accuracy and playability, and also (really important for us) coherent with the criteria of the rules about penalties for units that change formation or reform.
On the other hand, feedback from some long term Napoleon's Battles players reported complaints about an excessive hardening of the rule. We have carefully read those reports, arguments and historical examples, and also taken into account that the new rule is substantially different than those in the previous editions. We have decided to release an additional optional rule which was considered during the testing phase and tried out quite extensively, but that was left out in the final stages of the revision and replaced by the actual one. Please check the new optional rule at amend section to read the optional interpenetration rule.
We would also like to state that deciding this kind of wargame rules based on calculations and individual perceptions from historical witnesses that wrote about some particular event (not thinking in giving figures or accurate details in case someone is trying to design in the future a rule for a wargame) is far from conclusive, although we have made calculations to check the validity of our assumptions whenever possible. But inevitably over a degree of our personal historical perception we have built our own interpretation of this kind of events and given more weight to one or another account to design the rule that is included in the 4th new edition. We are convinced that the old free interpenetration should not be allowed by this new edition, but if players prefer to use the optional rule (that considers a softer penalty) they should be allowed to do so. We try to keep in mind that this is a game and should be an enjoyable experience (remember Bob Coggins catchphrases), and it is true that deciding the degree of penalty in a grand tactical game is as difficult as deciding movement rates or other averaged quantities. Both rules are reasonably accurate and simple, so we let experienced players to choose one or another. This twin rules could coexist the same way that the two wheeling rules coexist. In both cases, we prefer the one from the standard rules over the optional (that's why they are in this order at the rulebook), but the optional rules are perfectly valid and players are free to choose either of them in their games.
Below you can find samples on how to use this new optional rule, with an short explanation on each picture about the movement and its cost (click to enlarge).
We would finally thank to all those have contributed in these discussions with very enlightening posts, articles and responses.