In my youth, Avalon Hill's 1958 classic Tactics II had a simple combat system. To "commit" your troops you moved into the enemy's zone of control. All units were worth "1" except armor that was worth "2". You were doubled if defending behind a river, on a beach, behind a bridge, or on high terrain. You calculated the odds, rounded down, rolled a single die and looked it up on a matrix (die roll on the vertical axis, odds on horizontal axis). Results were either somebody died, both died, or somebody retreated. I was young then, with an agile mind. You could calculate the exact chance of any outcome; wargaming was a science. The combat system taught me the laws of independent chance (helpful if playing roulette or craps I might add).
Now I am old, my mind less agile, and I am confronted with the rather obtuse combat system in GGWBTS. Although I have certainly not mastered the system, as my contribution to your enjoyment, let me offer this brief guide.
Preliminarily, allow me to suggest, dear reader, that you accept the fact that without the algebraic formulas necessary to calculate (add, subtract, multiply, divide, mash, dice, and grate) all the factors used in combat resolution you will never, ever be able to replicate the specificity of likelihood of results available to Tactics II players in 1958. Count this a blessing. If you knew the formulas and actually used them your level of enjoyment would be roughly equilavent to filling out an income tax return with all schedules; the game would seem more like a job than a joy.
My suggestion is accept that wargaming in GGWBTS is an art, not a science. Let intuition be your guide. Have fun.
Land combat in GGWBTS has three components after movement: commitment, tactical combat resolution, and victory determination.
Commitment is discussed in section 10.1.2, pages 111 through 113. "Commitment" is a new concept to most boardgamers/computergamers, although a common feature of table top wargaming. The specific formula is not given. The main factors are described without relative weights being provided. Be intuitive. Assume your prejudices are correct until empirical proof suggests otherwise.
To participate in tactical combat resolution (rolling dice to hit people) attackers and/or defenders must be "committed". Sounds like some other dynamic I can think of but won't go into now.
1. The first positive factor listed (and thus presumably the most important) is the AC that provided initiative to the unit's commander is in the same region as the battle.
Other factors that will increase chance of commitment include:
2. TC with initiative linked to unit's commander.
3. If your side outnumbers the enemy(reverse if you are outnumbered).
4. A high command rating.
5. A high attack rating (for attacker; defense rating for defender).
6. Unused movement points.
7. Population and regional fortifications (presumably for defender).
Negative factors that decrease chance of commitment include:
8. Militia and mounted troops.
9. Forest, mountain or swamp terrain.
Tactical Combat Resolution is discussed in section 10.1.3 (called combat execution) at pages 114 through 116. Old time table top wargamers will remember throwing lots of dice in combat resolution (known in the hobby as "buckets of dice"). That is exactly what happens here. All those units are lining up and throwing dice to kill each other.
Section 5.0 describes the number of dice each unit rolls (fewer dice if defender is armored).
The total of all the die rolls is modified to a maximum +6 or -6 according to the factors listed at pages 114-115. Note that big modifiers include being unsupplied, taking fire previously and cover such as entrenchment and forts. Like I said, this is intuitive stuff but in this case it reflects the speciific prejudices of the designer.
The net result is compared to the defense value (again at section 5.0 and on the bar at the top of the map screen). In addition to regular "hits", the non infantry, non militia types are subject to a small chance of a critical hit (page 115), which I presume are caissons blowing up or the horses running away. If none of the above, if the attacker's net die total is at least 10% of the defense value, the defender suffers attrition in increments of 10%.
Victory determination is described in section 10.1.4 at page 118.
This is the simplest calculus.
1. The combat value (section 5.0) is halved if the unit is damaged or unsupplied (see how often supply factors in).
2. The commander's attack or defense rating is added (as appropriate).
3. Combat value is multiplied for entrenchments; forts add 10 or 40 to the combat value, doubled for heavy artillery.
4. There is an undisclosed adjustment for AC or TC
Feel free to savagely but constructively criticize anything I stated incorrectly.
Consider that more than 600,000 Americans died during the ACW. Such a war fought today with our present population and casualties in the same proportion would produce roughly 5,000,000 dead Americans. Clearly those folks were committed.
Starting in 1866 communities spontaneously honored their dead. From that people's movement came the holiday we know as Memorial Day. Honor the memory of those that sacrificed everything in defense of their country. Offer a prayer tonight for our young people that curently risk everything for the defense of our country.
"L'audace, l'audace, toujours l'audace."