Air combat: What does "evasion" and "interception" mean?

[reddishrecue]

Thats true. Most fighters dont evade even stealth/jet fighters wont evade sometimes.

 

[beetle]

Never seen any effect of a fighter group in the city that is being bombed. Are you sure?

My usual habit is a single fighter in the city being bombed. I can't vouch for the animation being triggered (or not) but said fighters routinely level up (after a bit) and bombers do die at pretty steady rate. If this usual habit of mine had no effect, I would like to think I would have picked up on it!

Just try it yourself: build a quick scenario where you can replicate the situation and see what happens.

I think the onus is on you to build the scenario, share the map, and make the case that fighters in cities don’t do the expected job. Like Delnar said, that is a pretty large bug for it not to be reasonably well known.

 

[Delnar_Ersike]

So the in-game values are either zero (everything but stealth bombers) or 100% (stealth bombers). That seems like poor design!
[...]
I had no idea Guided missiles could be intercepted. That just makes a weak unit even weaker! I almost never bother with them. Does anything else get an evasion chance?

Stealth Bomber, Guided Missile, and Nuclear Missile both have 100% evasion. Atomic Bomb has 50% evasion. I don't know of any other units off the top of my head who have evasion.

I honestly have no idea why Firaxis decided to half-heartedly remove evasion mechanics, though I suspect it may be related to an attempt to reduce combat randomness.

None of that makes sense to me. An Air Sweep just cancels out an intercept attempt for a tile -- nothing ever takes damage (not the plane sweeping, not the AA gun being sweep). So how is a +25% strength boost applied to 0? How is the Dogfight promotion not useless?

Air Sweep forces out the intercept, it does not cancel it: it causes the first interceptor to intercept the unit performing the air sweep, but the air sweeper gets a 25% bonus to their combat strength. Even when the air sweeper deals no damage to the interceptor (because it's a not an air interceptor, eg. it's a Destroyer or an AA gun), having a higher combat strength means the air sweeper takes less damage from the interception.

There was a discussion years ago about it, somewhere in these forums... a few people confirmed the rarity.

Just try it yourself: build a quick scenario where you can replicate the situation and see what happens.

It's actually really hard to replicate because the AI never sends out air units to intercept or to air sweep, so I'd need to set up a hotseat game with an editor.

 

[wayneb64]

Not sure why it would be hard to setup. The AI seems to always target cities first with it's bombers regardless of whether it has units to actually take the city. Now getting the AI to keep it's bombers near your city is another problem. It seems it always needs to shuffle all it's planes around every turn rather than actually use them.

 

[Delnar_Ersike]

Not sure why it would be hard to setup. The AI seems to always target cities first with it's bombers regardless of whether it has units to actually take the city. Now getting the AI to keep it's bombers near your city is another problem. It seems it always needs to shuffle all it's planes around every turn rather than actually use them.

Just did a test, had 3 Jet Fighters set to intercept in a 15 strength city that was going to be attacked by a bomber and a jet fighter. The bomber died, the enemy Jet Fighter went down to half health, and both of my Jet Fighters gained 2 XP.
Result: my Jet Fighters intercepted the enemy bombing runs even though they were located in the city.
Conclusion: the bug does not exist.

 

[wayneb64]

Just did a test, had 3 Jet Fighters set to intercept in a 15 strength city that was going to be attacked by a bomber and a jet fighter. The bomber died, the enemy Jet Fighter went down to half health, and both of my Jet Fighters gained 2 XP.
Result: my Jet Fighters intercepted the enemy bombing runs even though they were located in the city.
Conclusion: the bug does not exist.

Well the animations didn't play I bet so there is a bug which makes players think the interception is not working.

 

[Aristos]

Just did a test, had 3 Jet Fighters set to intercept in a 15 strength city that was going to be attacked by a bomber and a jet fighter. The bomber died, the enemy Jet Fighter went down to half health, and both of my Jet Fighters gained 2 XP.
Result: my Jet Fighters intercepted the enemy bombing runs even though they were located in the city.
Conclusion: the bug does not exist.

Nice that you got it going.

Conclusion: there is a bug in the animation that can make it seem the interception does not occur.

I cannot remember seeing the effects of the invisible interception, but I can concede that I probably did not pay attention.

 

[beetle]

Atomic Bomb has 50% evasion. I don't know of any other units off the top of my head who have evasion.

Yes, so zero or 100% -- really poor design. The A-Bomb 50% could be zero or 100% and it would not matter. From your previous post, failing to evade just means a chance to be intercepted. But a healthy strong single use unit being intercepted won’t be killed -- so intercepted or not is irrelevant.

Air Sweep forces out the intercept, it does not cancel it: it causes the first interceptor to intercept the unit performing the air sweep, but the air sweeper gets a 25% bonus to their combat strength. Even when the air sweeper deals no damage to the interceptor (because it's a not an air interceptor, eg. it's a Destroyer or an AA gun), having a higher combat strength means the air sweeper takes less damage from the interception.

My fighters air sweeping never take damage. Is this because the AI never puts fighters on intercept duty? So the Dog Fight promotion is useless in Single Player?

 

[Delnar_Ersike]

Conclusion: there is a bug in the animation that can make it seem the interception does not occur.

Possible; I had quick moves on in my test scenario, so I could not tell. I'm hoping that it's not engine bug, which would mean modders can fix it.

Yes, so zero or 100% -- really poor design. The A-Bomb 50% could be zero or 100% and it would not matter. From your previous post, failing to evade just means a chance to be intercepted. But a healthy strong single use unit being intercepted won’t be killed -- so intercepted or not is irrelevant.

Remember that Civ5 is built on top of a lot of Civ4's code, and Civ4 had a lot of interception-evasion chances (eg. Mech. Infantry had 20% intercept, bombers usually had a bit of evasion, etc.). This was because a) Civ4's combat system was more focused around lots of units, so a single lucky evasion or interception did not make as much of a difference as it would in Civ5, and b) Civ4's bombers could pillage improvements at range, which meant that designers needed to give a lot more units minor chances at air interception to defend against this sort of economic warfare (improvements were responsible for a majority of a city's yields, especially Town improvements that would take forever to rebuild if they ever got pillaged).

My fighters air sweeping never take damage. Is this because the AI never puts fighters on intercept duty? So the Dog Fight promotion is useless in Single Player?

Correct, the AI never puts fighters on intercept duty (theoretically it should, but it never does in practice) and also never air sweeps with them, so Dogfight is a nearly useless promotion in singleplayer unless you're playing with an AI mod. The two big AI mods I know of, Ninakoru's Smart AI and my Artificial Unintelligence, both attempt to address the issue with mixed results (ie. it's better, but not perfect); all other AI mods that I am aware of are based on one of these two mods and usually don't touch the code that's responsible for air sweeps and intercepts.

 

[wayneb64]

I absolutely positively saw my tri-planes defending the city they where in last night while playing. Full animations. Tri-planes are not the most reliable, but mine did have the sortie promotion so they got two chances to fail instead of one.

 

[reddishrecue]

sortie promotion any good?

 

[wayneb64]

I pretty much only use tri-planes/fighters for interception so it makes one plane as good as two. Since the AI pops out planes like pop-corn it helps thin them down much faster. Of course you need to get Brandenburg Gate so they can have it off the production line.

 

[beetle]

The sortie promotion is great, but I recommend taking air-repair first. Often, if I take sortie first, a fighter on constant intercept duties will die to attrition if I don’t give it a break.

 

[wayneb64]

On Immortal I have never even noticed any damage to my interceptors and getting two intercepts is crucial as space on the carrier is often limited, not to mention potential oil supply issues.

 

[wayneb64]

On a different note, I actually was very surprised that twice my bomber was actually intercepted by an AI defender. Did they sneak some kind of patch in as that has never happened to me before. I don't normally use bombers, but the situation I was in prompted me to give them a try.

 

[Delnar_Ersike]

On a different note, I actually was very surprised that twice my bomber was actually intercepted by an AI defender. Did they sneak some kind of patch in as that has never happened to me before. I don't normally use bombers, but the situation I was in prompted me to give them a try.

The intercepts happen if the AI fighter is not sent out to attack a target and does not wish to rebase to another city. This combination of events is rather rare, but not impossible. The AI does not consider holding back fighters for intercept duty when choosing targets to attack, and fighters tend to want to rebase if there are no nearby targets to attack; if the fighter is not sent out to attack and also does not wish to rebase, only then will it be put on intercept duty. Air sweeps also have code, but it never activates as a result of the weird interplay of AI systems that it relies on (short version: Air Sweeps rely on something only units in operations keep track of, but air units are almost never included in operations, so the air sweeps never happen).

As a side note, because of how little downtime air units get between attacking targets, fortifying to heal, and rebasing, the AI usually has serious issues upgrading them because by the time it gets around to its "upgrade" HomelandAI move, all of its air units have had their turns ended (when the AI chooses to fortify with a unit to heal it, it will prematurely end its turn, so there's no room to reconsider if a possibly better TacticalAI or HomelandAI move, eg. upgrading, pops up later on).

 

[beetle]

On Immortal I have never even noticed any damage to my interceptors and getting two intercepts is crucial as space on the carrier is often limited, not to mention potential oil supply issues.

Okay, I was thinking of cities with a single fighter coming under repeated bomber runs. That does not happen much to carriers because you can keep them out from line of sight.