Amphibious Units, or, are the laws of combat mechanics different for Marines?

Quintillus

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Over the past 24 hours, I have come across multiple interesting threads advocating unorthodox beliefs about amphibious units. I have not yet had the chance to conduct a trial on the legitimacy of these new pieces of information, but wanted to write down what I have heard and tie the threads together so that, should I forget about amphibious units after going to sleep tonight, there is still a trail to the evidence.

The first thread is this one; see especially posts #18 and #19, and the sources they link to. Post #18 quotes Sulla, who wrote, "Their [Marines'] special ability is to attack cities from ships, during which they ignore city defensive bonuses." Post #19 quoted alexman writing at Apolyton in 2004: "OK, the amphibious bonus is actually 25% (confirmed by Firaxis)." It's worth noting that by the time Civ IV was published in the fall of 2004, alexman was a Firaxis employee; I am not sure if he was at the time of that post. I am skeptical of both claims, given the lack of additional citations and that they do not appear to be common knowledge.

The Firaxis editor's help says of the Amphibious trait, "Units may attack from a ship onto land", saying nothing of what Sulla or alexman wrote.

@MeteorPunch did some tests in this post, which asserts to refute Sulla's claim. Though the results seem to support that, and the methodology appears sound, no sample size was given. It also doesn't necessarily contradict what alexman said; a 25% bonus would be more difficult to detect.

Next, some astute observers noticed an extra defensive field for buildings in my editor versus Firaxis's. I dug into it, and the differences suggest that the extra field may be intended as a buff against amphibious attacks. It also has a value of 50 for the Coastal Fortress in the standard Conquests game, suggesting that cities with a Coastal Fortress may have a significant advantage against seaborne Berserk and Marine attacks. It is unclear at this time if this field is one that Firaxis has planned, but never implemented, or if like charm, is is implemented, but hidden from the editor.

I thought it made sense to have a central thread on these, since there are significant implications if any of these possibilities stand up to scrutiny, and the topic may be of interest to more than just the people visiting the threads where the topic has already come up.

If you do any studies on these, please post the results. Hopefully we can follow the scientific method and determine once and for all if there is any merit to any of these possibilities.
 
To clarify:

Sulla said that Amphibious units ignore City Defense Bonuses. I believe that my testing showed that was not true, at least in Conquests 1.22. That may have been an undocumented feature at the time he wrote what he did.

The Firaxis employee, Alexman, said Amphibious units have a 25% attack bonus - another undocumented feature. That part could be true, I have no clue.
 
... Um, Gents - from Alexman's complete post:

AU mod: Amphibious Units

January 6, 2004, 18:26



The problem:

As mentioned in the Naval Bombardment thread, the C3C AI prefers to bombard cities instead of resources, even when it doesn’t follow up with ground or amphibious attacks. The units bombarded by the AI heal in the next turn, often resulting in no damage suffered by the bombarded civilization. On the other hand, if you leave your cities undefended, the AI will not bombard them, which encourages the counter-intuitive strategy of leaving coastal cities undefended until Marines (or Berserks) are available. The AI, of course, does not follow this strategy.


Possible Solution:

Add the Amphibious ability to Musketmen, Musketeers, Riflemen, and Infantry. Add the AI offense flag to Musketmen and Musketeers. Even units with a low attack are enough to discourage players from leaving cities undefended or lightly defended.
Remember, units have their attack factor doubled in amphibious assaults.[...]
 
Remember, units have their attack factor doubled in amphibious assaults.[...]

Huh?

Further down:
You're sure about that one? This would mean that Berzerks attack with an amphibious strength of 12 at the moment!
Sorry, it was among the changes that were mentioned before C3C was released, so I assumed it was true.

However, I just tested it and it's not true after all. So forget giving Musketmen an offensive ability! Next idea!

Seems that was either taken from an early build, or a misunderstanding of the logic (amphibious attack value is not halved when attacking across a river, so double what it would be otherwise...)
 
I fixed the link for the thread Alexman was referring to in the quote from Apolyton that WildWeazel made; it links to this thread. In post #357 of that thread, roidesfoux (king of the crazy? if my French is accurate) questions the claim of doubled amphibious attack, noting:

roidesfoux said:
I have not been able to find anything about this in the editor, the civilopedia, or in the forum. Can anyone verify or refute this claim?

This leads me to suspect the doubling claim was either a misunderstanding, or perhaps from a pre-release test build.

More testing is still needed, but alas, I am too tired even to play a few turns of the Assyrians in The Ancient Mediterranean tonight.
 
(amphibious attack value is not halved when attacking across a river, so double what it would be otherwise...)
(After searching C&C for threads with "amphibious" in the title) This is now the third time today that I have read this (unsourced?) assertion, or something along these lines.

But as I understand it, the river provides an additional defence-bonus to the defender, rather than reducing the attacker's attack-value per se? And the D-bonus is actually only +25%(?). According to this thread, anyway...
 
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In CCM 2.50 all modern amphibious units have a doubled attack, but only when attacking from board of ships into landterrain. The reason for this is a special combination of terrain movement handicaps set to zero and the blitz flag.

LVT7.jpg
 
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In CCM 2.50 all modern amphibious units have a doubled attack, but only when attacking from board of ships into landterrain. The reason for this is a special combination of terrain movement handicaps set to zero and the blitz flag.

View attachment 601733

"Double attack" as in attacking twice?

How do you limit the blitz attack to just from ship to land terrain? All terrain handicaps are eliminated by roads. These blitz units can still run fast and attack multiple times in roaded home turf.
 
Yes, attacking from road to road terrain is an exception, but attacks from board of a ship into city terrain (what these units should be used for) with normal settings (no roads in coastal terrain) never is a road to road attack.
 
How do you limit the blitz attack to just from ship to land terrain? All terrain handicaps are eliminated by roads.
But not when on enemy land-tiles!

And in CCM, IIRC, all land-terrains have a movement cost of at least 2 (possibly 3, I forget), so even M=2 units will only ever move 1 tile on enemy territory, unless @Civinator has decided otherwise, by allowing them to ignore those movement costs.

This means that CCM M=2+ units can be either 'fast' (e.g. most Horse- and Oil-powered units) or 'slow' (most [all?] bombard-units), but even the slow M=2 units may still retreat if they get redlined while attacking M=1 targets.

So a blitz-capable amphib unit which does not ignore terrain move-cost would be allowed to make 2 attacks from the ship, but once the last defender falls and the town is taken, those Marine units will be restricted to 1 attack per turn going from land-tile to land-tile (on enemy territory).
 
So a blitz-capable amphib unit which does not ignore terrain move-cost would be allowed to make 2 attacks from the ship, but once the last defender falls and the town is taken, those Marine units will be restricted to 1 attack per turn going from land-tile to land-tile (on enemy territory).

:yup: Yes, this is the philosophy behind this setting (the best is to reboard the marines back to ships after capturing a town and to attack the next cities or enemy units at the coast). On "home" terrain, the road to road attack problem remains, but the (in small numbers) autoproduced marine units are to precious to use them for such duties, that normal tanks can perform, too.
 
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