There are real limits to how far Catapults and Trebuchets can perform against Castle cities with +125% defenses.
Collateral Damage only
goes up to 50% max of the defenders hp for Catapults and Trebuchets.
The player can get enemy units down to half hp if their Cata/Treb has the same base
or more than the defender's base strength
To illustrate this, here are some nice looking
Collateral Damage Tables:
The most collateral damage Catapults can do to Longbows is get them down to 3.3/6 hp.
The most collateral damage Trebuchets can do to Longbows is get them down to 3.6/6hp.
Neither can hit Longbows with max 50% collateral damage, because Longbows have a higher base strength(6
) than Catapults(5
) or Trebuchets(4
)
Cannons with a base strength of 12 and a max collateral damage of 60% hp can get Longbows down to 2.4/6 hp, far superior to the Trebuchet which hits its limit at 3.6/6hp.
That is why people so often spend 60
to upgrade their Trebuchets to Cannons.
Units with identical base
such as Longbows, Swordsmen, and Crossbows (6
) receive the same amount of collateral damage.
There is no need to include every unit in Civ 4 to construct good tables.
The Chinese unique unit Cho-ku-nu (6
) has a strength of 3
when calculating Collateral Damage which makes for really pathetic collateral damage, but they can do it from the sea amphibiously off a transport which regular siege can't do.
They can also get Guerilla III for 50% withdrawal, so they can retreat and still inflict collateral damage.
All the Barrage promotion does is cause the Siege to do
more collateral damage racing to the limit faster.
Compare the Catapult with Catapult having Barrage I and Barrage II promotions.
City Raider is almost always
better than Barrage due to survivability unless attacking an enemy stack outside a city.
Barrage Catapults are for when the enemy has a huge stack outside your city and you need to soften them up so your Horse Units have much better odds to successfully perform flanking attacks and destroy enemy Siege units.
A few Barrage II and Barrage III Catapults also shine when suicide attacking a city with lots of promoted units and +100% defenses.
The trebuchet attack will also be suicide just like the Catapults, but the Barrage Catapults will do more overall damage once you factor in their costs of 50
vs. 80
In case anyone was wondering,
injured 0.1hp Catapults inflict FULL collateral damage.
It also does so against up to 6 other units in the stack with the defender.
Defense modifiers like +150% to defense do not affect Collateral Damage in any way.
Only the Base Strength of the attacking Siege Unit and the Base Strength of the defending unit matters when calculating Collateral Damage.
======================================
Now some people complain that they only hit 2 or 3 other units with collateral damage and not the full 6 with the Catapult or the full 7 with the Cannon.
That is because of 2 reasons.
First, if the defender has
Siege Units like Catapults, Trebs, or Machine Guns, they are immune to collateral damage and will absolutely soak up Collateral Damage hits.
Put 8 defenders in a stack of 60 Catapults, and you will see only 1 Collateral Damage inflicted occasionally.
2nd,
injured units below the Collateral Damage threshold will also
soak up Collateral Damage hits and make them vanish.
But not as often as you'd imagine.
This seems right.
This seems weird.
24 injured units and 8 healthy units.
A cannon doing Collateral Damage to a stack of 32 with 24 critically injured units
would be expected to hit the 7 healthy units with Collateral Damage 22.5% of the time.
Instead it occurs 78.6% of the time!
I thought this might be a mistake, so I made a new stack of 8 healthy Rifleman and 64 critically injured Rifleman.
Surely I
might get collateral damage to 1 healthy Rifleman each Cannon attack.
Guess how many I got?
4 or 5!
So a few very injured units will also soak up Collateral Damage hits, but only 1.
If there are a huge amount of injured units, they will soak up 2 Collateral Damage hits or maybe even 3, but not more.
Hopefully this clears up siege warfare confusion a bit for some people.