Commercial wargames began in the late 1950s as much simplified versions of systems used by professional soldiers for over a century. Unlike the professional games, those first commercial designs from Avalon Hill were actually historical simulations. The professional wargames concentrated on fighting tomorrow's battles, not yesterdays. Moreover, the professional games concentrated a lot of effort on tactical and operational level operations, while the first commercial wargames were largely strategic level.
There was a reason for this, and the reason was simplicity and accessibility. The professional wargames were complex beasts, requiring many hours of work to master, and equally long hours to play through. The commercial games had to be much more accessible. Even though these games were being bought by an upscale market of well educated men and teenagers, no one would have bought a game done to professional military standards. It was quickly discovered that commercial success meant a game that could be learned in less than half an hour, and played in two or three.
The early game designers were not concerned so much about complexity as they were in making the game historically realistic. This was not as easy as it looked, but most of the development effort went into creating a simulation that could, with reasonable (or at least convincing) accuracy reproduce the historical event it represented.
But then something unexpected happened. As gamers played more of the early games, they became adept at easily handling game procedures that scared off most of the population. Gamers trained themselves, by simply playing a lot, to a level where they could easily handle more complex procedures. Designers, being experienced gamers themselves, also became adept enough to create more complex games that did not collapse under mountains of procedures. The more complex games could thus cover more detail in the historical situation, but too often the more complex games were, well, simply more complex.
Then something less unexpected happened. The more complex a game was, the fewer copies were sold. Many experienced gamers who were capable of dealing with the more complex games decided that, for them, life was too short and they would just stick with the simpler games. Thus, after the first wave of complex games appeared in the mid-1970s, there was something of a backlash as gamers snapped simpler games in large quantities.
I always preferred to add as little complexity as possible to a design, in order to achieve additional (or necessary) realism or play value. I've designed a few complex games, and don't remember the process, or the results, fondly. It always seemed much ado about not much. But I was in the minority among game designers, and after I left the business in 1980, the designers of more complex games predominated. Many went on to design rules for miniatures games, an area that concentrated on detailed simulation of tactical operations.
The point of a historical simulation is to replicate the decision making process of the two commanders. This has more to do with things like decision cycles (which vary from army to army and period to period) and customs and habits among commanders (ditto.) One reason people preferred games that featured outstanding military leaders was that these guys had, in effect, "special powers." They didn't play by the rules historically, so you had to invent new game procedures to replicate the additional capabilities these Great Captains brought to the battlefield. Wellington simplified this effect somewhat when he said "Napoleon was worth 40,000 men." Napoleon was more than that, but it's true that his skills often had the same effect as giving a less able general an extra army corps or two. But a good designer would want to capture those specific skills of Napoleon (insight, speedy decision making, inspiration to troops and commanders alike, and so on) in his design. Other Great Captains would bring a different mix of magic to the battle, although I have found that there is a limited menu of skills for Great Captains to choose from. Still, players enjoyed seeing that kind of specialization.
Through the 1980s and 90s, designers concentrated on items that had previously been hidden from view. But this was often at the expense of simplicity. The details, real or imagined, of mechanized operations, intelligence play and psychological warfare became popular items for designers to spotlight. A game that paid a lot of attention to things logistics was a hard sell, even to the most experienced grognard.
The collapse of the wargame market in the 1980s gave designers an incentive to be even more creative, and they were. There was a lot more innovation in game design, and close attention paid to the shrinking pool of customers. Complex procedures were simplified and new game mechanics were used to keep pla