What Are the Optimal Ranks for Units?

[IPoseTheQuestionYouReturnTheAnswer]

I deploy my Janissary Heavy Infantry in ranks of 5, I assume this would work with sword infantry too. In MTW I used to do 4, but in M2 5 ranks seems reasonable with the improved cavalry. This way, enough Janissaries always survive to fight or defeat the cavalry, or at the very least hold them there long enough for my own heavy cavalry to flank.

Musketeers and archers I deploy in ranks of three. I believe that was the MTW optimum deployment too, so I just carried it over. This is very weak for melee, so if you're using horse archers, make sure to form them in thicker ranks (I usually do 4) before charging.

Cavalry I deploy in ranks of 4. 3 makes the line too thin, and it's easy to break with infantry. 4 ensures that there is enough momentum to break the line but still enough horses to keep fighting if the first rank is killed. This also makes it easier to break them off and recharge, since less of them are exposed and thus less will die when they turn their backs to reform. With 5 ranks, not enough men are fighting and thus it turns into a meat grinder where one rank is killed, the next advances, that is killed, etc.

[PaulTa]

For maximum firepower, I deploy muskets and crossbows in ranks of two. This allows the crossbows to fire at their targets more accurately, given their flat trajectory, and allows muskets to reload and fire at a greater rate.

Cavalry and infantry are almost entirely situational. If I'm on the plains with a mostly straight line of enemy infantry, I'll deploy my charging cavalry in a 2 deep formation. This guarantees that my cavalry will do the most damage possible with their charge. If I need to navigate cavalry around, or charge a specific unit, then a more norrow formation is generally recommended.

Infantry are dependant on their use. If the infantry unit is a bunch of spears about to absorb a cavalry charge, then I'd want them in a deep formation (usually a square). If I'm using melee infantry that I want to do the most damage possible with, then a wide formation. Same as cavalry, a smaller formation is used when I need the infantry to serve a specific function (such as navigating past a unit of spears and flanking an enemy unit).