There are many little bugs in the game, as mentioned by theov, however, his first two aren't bugs, they are just a case of idiotic AI, the same issue which has cursed the entire series of Civilisation games, and this isn't a bug, this is the design. Solving the AI to be something intelligent would be to make a completely different game where you wouldn't even need so many difficulty levels, it'd be like human vs human on Regent.
The AI can make successful naval landings, I've had 12 Cavalry arrive on a small island before, it's just more noticeable with islands because the AI doesn't know how to use foot units, but give it Cavalry and it can spam those at you and destroy you in seconds, land or sea. If the AI also knew how to make Cavalry Armies then no-one would ever win anything above Emperor. Imagine the AI pumping Military Generals every 3 turns without having to pay for them...
But the biggest problem I have with Civ 3 is still the military RNG. Darski bleated on about it for years and I also am not adverse to droning on about it, but all you ever get round here is people telling you to build Artillery, farm Armies and win. While this is great advice and does work really well, it is two kinds of cheese, both of which are designed to circumvent the whole point of units in the first place.
is a
meme for a very good reason.
At 4000BC you have the following units available to you (depending on traits):
Warrior 1.1.1
Spearman 1.2.1
Archer 2.1.1
Chariot 1.1.2
+ Unique Units, anything from 1.1.2 to 2.3.1
Moving on just one line of Techs and the number 3 becomes a lot more prevalent with some Unique Units getting up to the number 4. But, essentially, the Bronze/Iron age is 1-3.
The Middle Ages are then all about the numbers 3 to 6 (with some minor Uniques breaking up to number 8).
But then the Indistrial Age is about the numbers 6-12 and the Modern Age 14-24, really quite massive leaps.
But the numbers don't
guarantee anything. There's no screamingly obvious huge advance you can make in the field of military advancement whereby, as a player, you can make a definite decision about how many of which type of Unit you need in what part of the Battlefield, other than one Elite Modern Armour will always defeat one Regular Warrior, either in defence or in attack. So you have to go all the way from the first tech in 4000BC all the way to virtually the last Tech in the Modern Age to attain one simple military guarantee. And this is the one solitary difference between Civ 2 and Civ 3 which makes Civ 3 less of a tactical game than Civ 2.
Why?
Because a tactician needs to know how best to assign their troops. A tactician needs to know how best to assign their gold-to-troop ratio. With such great uncertainties in Civ 3 this becomes virtually impossible, because nothing adds up. It's virtually impossible to make your combined attack/defence economically viable, you almost invariably always have to go either all out attack or all out defence. Because if you leave one Mechanised Infantry defending your border town then a group of Cavalry can still over-run it quite easily. Leave 2 Mechs and the Cavalry can still over-run them relatively easily. Leave 3 Mechs in a town and you soon run out of units to attack with due to lack of Gold. Choose a Military Government System to compensate and your research drops to a snail's pace, not an option for any victory condition except Military Victories which still then run the risk of slowly becoming out-Tech'ed which hinders the Victory Condition.
But if becoming out-Tech'ed means you have weaker armies, aren't I acknowledging that the numbers mean something? Of course the numbers mean something - en masse - it's the fact that they don't mean anything
individually that is the problem. Let me explain with an example:
1. How many Archers do you need to Kill three Spearmen Fortified in City on a Hill? Let's say the Spearmen are two Veterans and one Regular. The Archers are all Veterans.
Now reverse this:
2. How many Fortified Spearmen do you need to defend a City from an invasion of 10 Veteran Archers?
For question 1 the minimum answer is 3. Three Veteran Archers can defeat 3 Spearmen, it can happen. But what is the maximum? Is it unlimited? Let's argue that 75% of the Archers inflict at least one Hit Point of damage and the first Archer fails to inflict any damage at all. One rough draft of this scenario produces a requirement of 23 Veteran Archers to defeat the three Spearmen. So the answer to question one is between 3 and 23.
For question 2, the maximum number of defenders you need is 11, but the minimum, even at the Archer's same 75% only doing 1 Hit Point and 25% no damage, is 2. So you need between 2 and 11.
And this is just for the first round of attacks. You'll need some attacks to fend off the invaders or you'll need some defenders to safeguard your new town from the inevitable counter-offensive.
So your attacking troop needs to be between 5 and 34 Units strong and your defensive troop needs to be between 5 and 34 Units strong. So in order to attack an opponents city in the north while defending your city in the south from an invasion while you're away you need between 10 and 68 Units (and this is just to cover the two cities in question, let alone an empire with sprawling weird boundaries.
There is no
correct decision a tactician can make as to the correct course of action as the variables are too wide. Which then effects your strategy, such as forcing you to trade a crucial Tech like Writing to the empire to the south to ensure peace, or, as is much more often the case, delaying combat until you have access to Mobile Units - which you won't even know about until The Wheel is discovered, making non-Horse starts extremely depressing, almost as depressing as Horse but no Iron or Saltpeter. Delaying invasion then gives the AI so much time to spam new cities everywhere that your 10 Horses suddenly look like chicken feed, looks like now you'll need 30 or 40, but, oh dear, you're neighbor's the Carthaginians, let's call the whole thing off...
So we either make spam for Armies to beat the impossibility of the uncertainty or we try our best to gain such a large Tech lead that we will need between 10 and 48 Units instead of 10-68 (but then the new Units cost more production, costing a fortune in upgrades or a depressingly slow creation rate, tempting one to then wait for Railroads and Factories) or we just spam the crap out of Unit Production and to heck with the Tech and Gold levels.
These are the three sole tactics which work in Civ 3. Armies, Tech superiority + high Productivity, or mindless Unit spam. None of which are what you would describe as 'tactical' towards a greater 'strategy', beyond performing a simple routine.
Watching 300 the other day, that movie is all about Choke Points. 300 Elites defending unlimited armies by means of funneling the enemy into a narrow passage. Can you do this in Civ 3? Nope, a group of Longbowmen can cut down a Rifleman Fortified on a Mountain (a whole Tech Age in difference) and it's actually worse of your defender starts out as Elite.
Watching Lord of the Rings the other day, does it matter if you line up a group of Fortifications? Nope, not really, Your lone Rifleman will still buckle under the pressure of a group of Longbowmen and, again, it's worse if he starts out as Elite. And the Fortification doesn't prevent the enemy just walking round it, it has no greater sphere of influence than one square. How many single square choke points do you get in a game of Civ? Hardly any, especially with those diagonals often making one square passable 3 ways.
In Civ 2 you could leave one Tank to act as attacker and one Infantry in your town as a defender and all the enemy could do was pillage until the Tank got round to killing them. Longbowmen would just die, no matter how many attacked, your Hit-Points would never deteriorate. A Rifleman in a Fortification would be the proverbial rock. In Civ 3 you seem to lose a Hit-Point with such incredible ease that absolutely nothing is guaranteed. Your Modern Infantry can be reduced to a red-line simply by attacking a Pikeman, leaving the Unit needing cover while it recovers, because you better not leave it in a town, because you'll rage when it flips on all your 2/3 Hit-Point recoverers - so how many units do you need to cover...? Gaaaaah.
And then two of your Cavalry die attacking a sticky Pikeman and your entire empire goes into revolt... nevermind that pre-mass media it took catastrophic failure of an entire campaign to cause this to happen, not just the loss of one or two posses in an otherwise utterly triumphant campaign.
It's all just such a complete mess, all in the name of 'balance'. If you ask me then the biggest glitch in the game is having no hard-coded barriers between different military Units of different eras, or, at least, a heck of a lot more thought put into what would be more 'tactically useful' for the player to enjoy a better
variety of tactics and therefore strategies.