...and medieval wars suck because longbowmen pwn.
Not only is the general trend of economic development and the tech tree set up to discourage medieval war (AI prioritizes machinery and guilds) and favor renaissance war (AI goes after constitution/democracy nonsense), but the relative defender/attacker unit strengths are just inviting the player to go offensive in the renaissance.
Let's consider each resourceless defense unit in comparison to each set of respective attackers that one usually faces. (When fighting the AI, let's face it, most of the garbage that you have to mow down consists of whatever era's resourceless defense unit. The AI simply does not spam defensive spears or axes or crossbows. Maybe a few. That's it. So the relative strengths of their resourceless defenders vs. your attackers is what is mostly going to determine victory or defeat).
Units will be compared from a basis of no promotions, but fortification is assumed in all cases for the defender. Also, where hill bonuses apply to the defender, we will assume that half of all cases will involve that bonus, so half of the bonus will be applied to the overall strength.
Late ancient/Early classical:
Archer: 3 * (+50% city def.) * (+25% hills def.)/2 * (+25% fortification bonus) = 5.625
vs.
Axe: 5 (ratio: 1.125)
Sword: 6.6 (ratio: 0.852)
Horsey: 6 (ratio: 0.9375).
Average ratio: 0.9715
Early classical wars have the added disadvantages to the attacker of:
*Slower/non-existent roads.
*Greater distances
*Economy not set up to handle acquisition of many new distant cities.
*Walls that won't be bombardable.
*Archer gets 1 first strike against 2 of the 3 main attackers.
Late classical/medieval:
Longbowman: 6 * (+25% city def.) * (+25% hills def.)/2 * (+25% fortification bonus) = 9.75
vs.
War elephant: 8 (ratio: 1.22)
Maceman: 8 (ratio: 1.22)
Knight: 10 (ratio: 0.975)
Average ratio: 1.383
On the bright side:
*You can now bombard away wall and cultural defenses.
*Closer borders
*Moar courthouses!
**Economy will be able to handle the war better.
*Moar roads! (and 3 movement points after engineering). Faster wars...(but more than compensated by those awful castles...)
On the downside:
*Longbows are freakin' tough! An average ratio of 1.383 times the strength of the most common attackers. The ratios are higher (longbows are tougher) against both the weakest attacker (1.22 vs. 1.125) and the strongest attacker (0.975 vs. 0.852).
*Longbows still get 1 first strike against 2 of the 3 toughest attackers.
Renaissance:
Musketman: 9 * (+0% city def.) * (+0% hills def.)/2 * (+25% fortification) = 11.25
vs.
Cuirassiers: 12
Ratio: 0.9375
Not only is this the lowest average ratio so far, but:
*Less rock/paper/scissors mechanics for the attacker to worry about.
*Defender does not get 1st strike
*Main attacking unit has an inherent 15% retreat chance.
*Economy fully ready for war
*Medieval castle nonsense is obsolete.
Everything is geared for going on the attack in this period.
Also consider:
*You can get 3 longbowmen (9.75, 1 first strike) for 150 hammers.
*You can get 2 musketmen (11.25, no first strike) for 160 hammers.
*You can get 3 musketmen (11.25, no first strike) for 240 hammers.
That seems like a steep jump in price for such a marginal increase in strength. Sometimes I almost feel like I'm getting a downgrade when I research gunpowder. It's no wonder that people like to either strike hard with cuirassiers or jump ahead to rifles. Who wants to turtle with muskets?!
To continue the comparison:
Industrial era:
Rifleman: 14 * (+25% fortification bonus) = 17.5
Grenadier: 12 * (+25% rifleman attack bonus) = 15
Ratio: 1.166
I'll calculate it separately for vs. cavalry:
Rifleman: 14 * (+25% fortification bonus) * (+25% vs. mounted) = 21
Cavalry: 15 (with 30% retreat chance).
Ratio: 1.4
Average ratio: 1.283
Once you make it to riflemen, your defenders once again get a very sturdy ratio vs. the attackers. Not quite as good as the medieval period, but close.
Once you get into modern warfare, the rock/paper/scissors stuff becomes ridiculous, even assuming only resourceless defenders, but let's just assume we stick with the draftable defenders:
Infantry: 20 * (+25% fortification bonus) = 25.
Tank: 28
Ratio: 0.893.
The advantage then shifts back to the attacker, except for the fact that you're now dealing with railroads, anti-tank stuff, defensive air patrols, possibly nukes, etc., making attacking actually relatively difficult.
Future era:
Mech infantry: 32 * (+25% fortification bonus) = 40
Modern armor: 40 (+1 first strike)
Ratio: 1
Plus, you are dealing with all of the aforementioned headaches of the modern era, times like a thousand.
So, by late game, it gets really really hard to go on the offensive without a tech advantage or a huge production advantage.
The nice thing about the renaissance period is, you don't really need a temporary tech advantage. You can pretty much fight at parity and win as long as you are the attacker, going cuirassier vs. musket. Some people like to try and go cav vs. musket, but then they often get unpleasantly surprised by "magic rifles," which are a HUGE jump up from crappy muskets.
That's why I'd say, if you are worried about the tech situation being close, cuirassiers are the name of the game! They'll do the job.
So here's how I would summarize a typical game, assuming tech parity all the way through:
Ancient/early classical era: Attack opportunistically, if you can take them by surprise and overwhelm them before they get more defenders/walls (because reinforcing your attack will be hard). And know when to stop.
Medieval era: Just don't. Or, only attack if you have a very good specific reason for it.
Renaissance era: Hurry, hurry, go for it! It's a small window, but it's your best chance to attack in the game, all other specific things being equal. (Of course, every game is going to be different. This is just a rough guide that assumes tech parity and no extenuating circumstances).
Industrial era: exercise caution.
Modern era: Finish up those last few campaigns with your tanks before things really start getting hairy!
Future era: War is hell.
To conclude, in my opinion, increasing the base strength of musketmen to 10 would balance the warring potential of the era, if that is desired, and would make the jump to "magic rifles" less extreme. Muskets might also then find some use alongside cannons as offensive troops as well, which is what they were historically (a dual offense/defense unit, a la the Napoleonic wars).
Another rule of thumb: any city defense unit should be able to attack and kill the previous era's defense unit. This makes it so that a player could theoretically compensate for not having any strategic resources by temporarily beelining a whole tech era ahead in military technology and pwn his/her neighbors. And this rule holds for every defensive unit except the musketman:
Longbowman attacks and kills city-fortified archer.
Rifleman attacks and kills city-foritifed musketman.
Infantry attacks and kills city-fortified rifleman.
Mechanized infantry attacks and kills city-fortified infantry.
But musketmen cannot attack and kill city-fortified longbowmen, on average.
If musketmen were increased to strength 10, then they could. And riflemen could still attack and kill musketmen.
Not only is the general trend of economic development and the tech tree set up to discourage medieval war (AI prioritizes machinery and guilds) and favor renaissance war (AI goes after constitution/democracy nonsense), but the relative defender/attacker unit strengths are just inviting the player to go offensive in the renaissance.
Let's consider each resourceless defense unit in comparison to each set of respective attackers that one usually faces. (When fighting the AI, let's face it, most of the garbage that you have to mow down consists of whatever era's resourceless defense unit. The AI simply does not spam defensive spears or axes or crossbows. Maybe a few. That's it. So the relative strengths of their resourceless defenders vs. your attackers is what is mostly going to determine victory or defeat).
Units will be compared from a basis of no promotions, but fortification is assumed in all cases for the defender. Also, where hill bonuses apply to the defender, we will assume that half of all cases will involve that bonus, so half of the bonus will be applied to the overall strength.
Late ancient/Early classical:
Archer: 3 * (+50% city def.) * (+25% hills def.)/2 * (+25% fortification bonus) = 5.625
vs.
Axe: 5 (ratio: 1.125)
Sword: 6.6 (ratio: 0.852)
Horsey: 6 (ratio: 0.9375).
Average ratio: 0.9715
Early classical wars have the added disadvantages to the attacker of:
*Slower/non-existent roads.
*Greater distances
*Economy not set up to handle acquisition of many new distant cities.
*Walls that won't be bombardable.
*Archer gets 1 first strike against 2 of the 3 main attackers.
Late classical/medieval:
Longbowman: 6 * (+25% city def.) * (+25% hills def.)/2 * (+25% fortification bonus) = 9.75
vs.
War elephant: 8 (ratio: 1.22)
Maceman: 8 (ratio: 1.22)
Knight: 10 (ratio: 0.975)
Average ratio: 1.383
On the bright side:
*You can now bombard away wall and cultural defenses.
*Closer borders
*Moar courthouses!
**Economy will be able to handle the war better.
*Moar roads! (and 3 movement points after engineering). Faster wars...(but more than compensated by those awful castles...)
On the downside:
*Longbows are freakin' tough! An average ratio of 1.383 times the strength of the most common attackers. The ratios are higher (longbows are tougher) against both the weakest attacker (1.22 vs. 1.125) and the strongest attacker (0.975 vs. 0.852).
*Longbows still get 1 first strike against 2 of the 3 toughest attackers.
Renaissance:
Musketman: 9 * (+0% city def.) * (+0% hills def.)/2 * (+25% fortification) = 11.25
vs.
Cuirassiers: 12
Ratio: 0.9375
Not only is this the lowest average ratio so far, but:
*Less rock/paper/scissors mechanics for the attacker to worry about.
*Defender does not get 1st strike
*Main attacking unit has an inherent 15% retreat chance.
*Economy fully ready for war
*Medieval castle nonsense is obsolete.
Everything is geared for going on the attack in this period.
Also consider:
*You can get 3 longbowmen (9.75, 1 first strike) for 150 hammers.
*You can get 2 musketmen (11.25, no first strike) for 160 hammers.
*You can get 3 musketmen (11.25, no first strike) for 240 hammers.
That seems like a steep jump in price for such a marginal increase in strength. Sometimes I almost feel like I'm getting a downgrade when I research gunpowder. It's no wonder that people like to either strike hard with cuirassiers or jump ahead to rifles. Who wants to turtle with muskets?!
To continue the comparison:
Industrial era:
Rifleman: 14 * (+25% fortification bonus) = 17.5
Grenadier: 12 * (+25% rifleman attack bonus) = 15
Ratio: 1.166
I'll calculate it separately for vs. cavalry:
Rifleman: 14 * (+25% fortification bonus) * (+25% vs. mounted) = 21
Cavalry: 15 (with 30% retreat chance).
Ratio: 1.4
Average ratio: 1.283
Once you make it to riflemen, your defenders once again get a very sturdy ratio vs. the attackers. Not quite as good as the medieval period, but close.
Once you get into modern warfare, the rock/paper/scissors stuff becomes ridiculous, even assuming only resourceless defenders, but let's just assume we stick with the draftable defenders:
Infantry: 20 * (+25% fortification bonus) = 25.
Tank: 28
Ratio: 0.893.
The advantage then shifts back to the attacker, except for the fact that you're now dealing with railroads, anti-tank stuff, defensive air patrols, possibly nukes, etc., making attacking actually relatively difficult.
Future era:
Mech infantry: 32 * (+25% fortification bonus) = 40
Modern armor: 40 (+1 first strike)
Ratio: 1
Plus, you are dealing with all of the aforementioned headaches of the modern era, times like a thousand.
So, by late game, it gets really really hard to go on the offensive without a tech advantage or a huge production advantage.
The nice thing about the renaissance period is, you don't really need a temporary tech advantage. You can pretty much fight at parity and win as long as you are the attacker, going cuirassier vs. musket. Some people like to try and go cav vs. musket, but then they often get unpleasantly surprised by "magic rifles," which are a HUGE jump up from crappy muskets.
That's why I'd say, if you are worried about the tech situation being close, cuirassiers are the name of the game! They'll do the job.
So here's how I would summarize a typical game, assuming tech parity all the way through:
Ancient/early classical era: Attack opportunistically, if you can take them by surprise and overwhelm them before they get more defenders/walls (because reinforcing your attack will be hard). And know when to stop.
Medieval era: Just don't. Or, only attack if you have a very good specific reason for it.
Renaissance era: Hurry, hurry, go for it! It's a small window, but it's your best chance to attack in the game, all other specific things being equal. (Of course, every game is going to be different. This is just a rough guide that assumes tech parity and no extenuating circumstances).
Industrial era: exercise caution.
Modern era: Finish up those last few campaigns with your tanks before things really start getting hairy!
Future era: War is hell.
To conclude, in my opinion, increasing the base strength of musketmen to 10 would balance the warring potential of the era, if that is desired, and would make the jump to "magic rifles" less extreme. Muskets might also then find some use alongside cannons as offensive troops as well, which is what they were historically (a dual offense/defense unit, a la the Napoleonic wars).
Another rule of thumb: any city defense unit should be able to attack and kill the previous era's defense unit. This makes it so that a player could theoretically compensate for not having any strategic resources by temporarily beelining a whole tech era ahead in military technology and pwn his/her neighbors. And this rule holds for every defensive unit except the musketman:
Longbowman attacks and kills city-fortified archer.
Rifleman attacks and kills city-foritifed musketman.
Infantry attacks and kills city-fortified rifleman.
Mechanized infantry attacks and kills city-fortified infantry.
But musketmen cannot attack and kill city-fortified longbowmen, on average.
If musketmen were increased to strength 10, then they could. And riflemen could still attack and kill musketmen.