Fortresses and PTW - An Interesting Result

[Catt]

Thanks to a toddler banging on my laptop keyboard before I finished a turn (and the resulting reload to replay my turn), I noticed something very interesting - so much so that it almost strikes me as an exploit (not sure yet - the discovery needs a bit more time to sink in).

First, the basics - two key points: (1) fortresses offer a 50% defensive bonus to units garrisoned there, and also offer ZOC ability to any units therein; and (2) PTW incorporated some clear differences in AI behavior (compared to vanilla Civ v1.29) which is particularly evident with the activity of barbarians -- from Firaxian comment, we know that the AI-controlled civs make a calculation regarding the odds of battle before committing troops to any particular engagement -- if the odds are heavily against the AI, it tends to break off an attack and/or look for a weaker target -- there's a lot less of the AI throwing stacks of inferior units against a superior tactical situation.

These two facts, and the intervention of my toddler, lead me to a startling discovery -- where the local geography permits, a maginot line can be far more effective than it was under vanilla Civ. It can seemingly offer real deterrence at very low cost, and enable a technologically advanced civ to maintain a very small standing army but still be secure within its borders.

I was playing an all-random game and drew the Ottomans as my civ. An ineffective Babylon offensive in the BCs secured for me the former Babylonian lands -- I had two decent but small cores established early, and from that point felt I could win in any fashion I chose. I have been experimenting with largely peaceful games, trying to focus a bit on trading and diplomacy, and I let the age of the Sipahi pass without offensive war (sacrilege, I know ). But my diplomacy was ineffective -- I found the Ottoman empire embroiled in several wars, and even with Universal Suffrage my Republic began to feel the strains. I constructed a longish maginot line before I finally decided to take a Persian city to encourage negotiations and also significantly shorten the needed maginot defenses.

In the age of infantry and tanks, just after entering the Modern Age (I had a 3 - 4 tech lead and no one except the Ottomans yet had tanks) I took Tyre from the Persians. I intended to build fortresses and staff them in the appropriate spots to insulate my new territory from incursions. After taking Tyre, but before I could build the defensive fortifications and attend to some pollution clean-up, I stepped away from the laptop and fate intervened. I returned to find a guilty but happy child and a screen that clearly showed that my turn had ended and the AI had moved -- a good-sized SOD waited outside my new city, and a dozen or so wounded and "retreated" cavalry were nearby -- I had also lost some key assets. I reloaded the turn, played it out as best I could as I had done the first time, but completed my planned fortifications and posturing. When I ended my turn, I was quite surprised to see not one whit of an AI SOD -- I suffered an aerial bombardment or two, but my maginot line was unmolested!

After finishing the game, I recreated the incident as best I could so as to grab some screen shots. Below is a screenshot that shows Tyre and its immediate surroundings on the same turn -- in the top view, my defensive fortifications are complete and unmolested after one turn; and in the bottom view is the situation when no defensive fortifications were erected.

In the "real" game I staffed the fortresses with 4 infantry each -- in the replay shown here, I tried it with only 2 infantry in each fort -- still no attack whatsoever! So . . . 2 infantry, fortified in fortresses on grassland, and within the defensive umbrella of a radar tower (defense of ‘21’ for each infantry), were sufficient to deter an AI SOD that consisted of +/- 10 dead cavalry, 10 wounded and "retreated" cavalry, and +/- 45 infantry and guerillas (mostly infantry). For the cost of some fortresses, a few radar towers, and less than 2 dozen infantry in total, I could have secure borders, no incursion of AI forces other than by sea ( ), and no increase in war weariness.

Interesting? Exploitative?

Catt

[Arrian]

Interesting? Yes.

Exploit? No.

-Arrian

[Jawa Jocky]

Thats NOT an exploit its just good strategy.

I never stopped to think about how powerful radar towers are when combined with fortifications. I never use them myself. Then again I don't play much in the modern era.

My bias probably comes from how I've played PTW in the modern era. Huge stacks of artillery bring every unit to 1 hp and leftover calvary kill them off. Tanks and MA take cities.

[wilbill]

Doesn't sound like an exploit to me. I just hope the AI doesn't do it to me. Taking a 13+ metropolis with a well defended radar tower adjacent on a hill is tough enough and the AI definitely understands that tactic.

[Catt]

Yeah - after sleeping on it, I don't think it can be classified as an exploit. I really like the AI's "smarter targeting and engagement decisions" under PTW, but at the same time it seems a bit of a shame that 2 infantry in a fortress with radar coverage can deter a stack of 60+ units.

Catt

[Jawa Jocky]

It's too bad the AI still can't use artillery effectively. It's so easy to punch a hole in a line like this.

Like I said earlier. I never noticed how effective this combination could be because I was using artillery.

[minke19104]

or tactical nuke

[Jaybe]

Originally posted by Jawa Jocky
It's too bad the AI still can't use artillery effectively. It's so easy to punch a hole in a line like this.
...

As I have mentioned before, with the current AI stupidity regarding offensive use of artillery, the only real balancer is to limit the player's use of ground-based artillery.

[Chemical Ollie]

I did that recently too. It works, allright - except if one of the tiles in the maginot line is a city. I had two 4-infantry armies in the city but the enemy cavallery kept on attacking and eventually captured my city. Well, I took it back on the next turn, but it was a hard blow. The 1-2 infantry fortresses were never attacked.

[Yahweh Sabaoth]

Hmmm, I guess the 8 infantry each I just placed in 2 fortresses, each on hills that form ithsmuses, to block Babylonian cavalry on Regent level are, perhaps, overkill.

[nbarclay]

If the AI has units with an attack value higher than six (tanks or the higher-attack-value infantry used in the AU mod), it can be willing to attack forts with more than just a couple infantry in them. In AU 203, an AI stack with infantry as its top units tried to attack a fort with at least four or five infantry in it, but the AI gave up when it lost a few units, didn't kill any, and eventually ended up getting one of my infantry promoted to elite without its taking damage. Later, single tanks occasionally hurled themselves at my wall (although the place they hit then may have been just a little less well-fefended).

Nathan

[Yahweh Sabaoth]

We'll see how those Babylonians treat me. They are fond of putting together 10+ cavalry in a stack, I've noticed... they attacked one city with 30 units! Oy vey!

(I hear this is a common number for you more "advanced" types to come up against, though)

[Odin]

Originally posted by minke19104
or tactical nuke

Then you'll be at war with everyone.

I only use a "Magnot Line" tactic when by land boarders are narrow, 6 tiles wide or less. If I have a lot of border on land I use a moblie defense force of mounted units or tanks instead.

[badams52]

Nathan,

Once your infantry upgraded to elite, the AI probably reevaluated it's chances of winning and found them too low so he stopped. Happened with me when the AI was attacking my pikemen on a mountain with his legionary in AU206. The pikeman didn't lose any strength, became elite and that stopped the attacks. He would attack with longbowmen though

[Catt]

Originally posted by badams52
Nathan,

Once your infantry upgraded to elite, the AI probably reevaluated it's chances of winning and found them too low so he stopped. Happened with me when the AI was attacking my pikemen on a mountain with his legionary in AU206. The pikeman didn't lose any strength, became elite and that stopped the attacks. He would attack with longbowmen though

Which suggests that someone could set up a test to try and determine if there are hard-coded break-points - and what those points are.

I did the math quickly on your experiences, and, making some assumptions, my guess is that there is a breakpoint somewhere in the "10% chance of success" range. Legions attacking a veteran pikeman fortified on a mountain have only a 13.6% and 7.7% chance of success for a veteran and regular legion, respectively. Once the pikeman is elite and uninjured, the chances of success drop to 6.5% and 3.3% respectively. By compariosn, a longbowman making the same attack against an elite would have a 23.8% and 14.3% chance of success.

In Nathan's example - with the AU Mod infantry attacking at 8 -- the chances of success against a veteran infantry fortified in a fortress on flat lands is 12.8% and 7.1% respectively. When the defender is elite and uninjured, the odds drop to 6.0% and 3.0%.

My own example (infantry with modified defense of 21 against "6" attackers) offers only a 4.8% chance of success.

The examples imply that with a chance of success at least in the low teens (12.8% or 13.6%, for example), the AI will attack; but when the chance of success drops to the mid-single digits (6.5% or 6.0%, for example) the AI ceases its attack.

Catt

I made a lot of assumptions: (1) that there is a hard-coded breakpoint; (2) assumptions regarding veteran attackers, Nathan's forts on flatlands, and badams52's pikeman without a fort; and, not least of which, (3) the civ combat calculator I used to generate the odds of succes is in working order .