Interpenetration and Displacement

In the picture below there is a formation of Spanish infantry made up of 1 S in front and 2 FL one behind the other. The question is how do the new interpenetration and displacement rules work. Imagine the front FL coming up and tapping the S (not fully occupying its space) causing the S to displace backwards such that the S sits partially on top of the back FL unit. What happens in this situation? In Impetus 2 units that interpenetrate from the front push the unit being displaced forward not backward as in Impetus 1. In this case pushing the back FL forward would either two potential results

A. It would push the front FL forward to make space for itself.

or

B. It would tap the front FL causing a chain reaction of never ending displacements.

If we discount B then seems that there only two real possibilities to create space for itself.

1. The Back FL displaces forward and pushes the front the FL forward in doing so.

2. The S moves all the way through 2nd FL until it finds space to be redeployed (as in Impetus 1.)

If 1 is correct that means that the sort of formation in the picture below would slowly creep forward towards the enemy as the units move through each other.

Any thoughts?

Gaius,
You know I love these questions (if they don’t happen in the middle of a game).
Your photo and scenario a slightly different. In the photo all stands are already touching and this is a “formation”. Your situation has the front FL unit coming up and tapping the S unit.
If they stands are already touching than the rule states:
“When S, T, FL, CL are interpenetrated, these automatically allow the interpenetration, moving behind the interpenetrating Unit after movement is completed…….The exception is when the interpenetrating Unit starts its movement in base contact with the unit it wants to interpenetrate. In this case the interpenetration is allowed even with one move action, allowing the crossing Unit to move more than normal.”
So if the FL Unit (with 2H) movement starts in contact it will pass thru and the S Unit will not even move.
Now if the FL Unit is not touching the S unit. “The Front FL coming up and tapping S”.Then the next paragraph :
”When dealing with interpenetration remember that:
b) If the interpenetrating unit approaches a unit from the side or rear and hasn’t got enough movement left to pass completely through the unit it is interpenetrating, the interpenetrated unit moves backward.”
I interpret this as meaning that you must use up to your full movement allowance to pass through a unit and not just stop. Even if the S unit was using the deeper base and The Fl unit was only able to move 1H, there would (should) still be enough room for the S unit to move behind.
So I don’t really see this happening however if the rear FL unit moves first, that is another issue but I will put that in a second post.

I think you are misunderstanding the scenario Scott. I will try again.

The front FL wishes to end its movement partially on top of the S. That forces the S to displace backwards. No problem there.

The S moves backwards but does not have enough space to fit in between the front FL and the back FL. Question? What happens to the S unit? It should stay where it is and force the back FL forward. Why, because it now sits on partially top of the back FL. The rules state that the back FL should displace forward because the S unit moves on top of it from the front edge. This is a change from Impetus 1. Again no problem here.

Here is where the problem arises. There is no room for the back FL to move forward and fit in. It will partially sit on top the front FL (which would cause the front FL to displace backwards.) Obviously this is not a solution because the whole cycle will continue ad infinitum.

What is the solution?

1. S continues to back of the column? This is the solution in Impetus 1
2. The back FL displaces forward and forces the front FL to move forward to create space for it.

Or another possibility which I didn't consider in my first posting.

3. The movement is prohibited because it cannot resolve itself.

Why is the Spanish player doing this? So that he can get maximum fire power against the enemy. He is rotating the three units through to get three shots at the enemy.

Hey Gaius,
Thanks for the clarification on your intent.
I was trying to send a second post with more on my thoughts. It did not go through so I will attempt it again.
I feel that the rules involving interpenetration talk about displacing units forward or back, when the active unit does not have “enough movement left to pass completely through the unit it is interpenetrating.” This indicates to me that if you have the movement available to move through, than you move through not stopping on top whether it, be a little or a lot. These rules seem to me to say that stopping on another unit is due to lack of movement not as a way to rotate front units in place.
5.11.1.1 Deals with a group firing front line T’s than second line FP’s interpenetrating, but the Group moved twice for firing purposes.
I know that we are dealing with Javelins and there isn’t a penalty for 1 Move and shooting but if the S were bows how would this affect them, shooting than being displaced on purpose.
There is a diagram on page 32 does not say if the FP used it available movement or not but it uses the word retreating for the T unit. Is this now a Forced move and follows the rules 5.11.2.
I will try to send my other post but in it I thought that 2 B was the way to go

Gaius,
You know I love these questions (if they don’t happen in the middle of a game).
Part 2
I attempted to send this earlier.
Looking at the possibilities of this situation, if the rear FL unit wanted to move through both the Front FL unit and the S unit, It could using more than one movement, ie regular movement and a march, but that is not the question here. Using 1 Movement the Rear FL would land on the S unit Forcing it back on top of the Front(now Rear) FL unit.
My quick answer to you is: B 2 the S unit moves all the way until it finds space to be redeployed.
It just seems reasonable that the unit backing up would be looking for open ground.
The more rule oriented me thinks that the Paragraph:
“When dealing with interpenetration Remember that:
a) The interpenetrated Unit can be forced to move forward…….Unit approaches it from the front doesn’t have enough movement left to pass completely through the unit it is interpenetrating”.
The unit falling back in this case the S Unit does not really have a movement allowance, it is simply falling back.
My gaming buddy uses large pike units 3 Stands (Units) deep. For 15mm this is 9 cm to 12 cm deep. A unit of FL being interpenetrated by this large unit would not have the Movement allowance to back up, they just do.
Also the unit being interpenetrated is not the active unit but is reacting to the active unit.
This was a very challenging question.

Hi Scott

What makes the interpenetration rules in Impetus 2 interesting and different from Impetus 1 is that the direction of interpenetration now influences which way the unit moves while being displaced. I think this is actually a good change but it does raise a few conundrums.

Imagine a scenario where the units in the photo are charged. The S unit evades back and the front FL fights. The front FL loses and retreats 1H. It lands right on top of the back FL. What happens in this case? The rules says that the FL being displaced should be moved forward not backward because the interpenetration is coming from the front. But technically there isn't enough room for the displacing FL (because it would literally touch the enemy unit.) What happens?

We have been playing it that the displacing FL moves forward almost to touching the enemy unit and the interpenetrating FL is placed immediately behind it. But the rules are silent on this.

Hello again
I am so glad we are having this discussion.
I am not really sure yet how I feel about a unit being forced forward by a unit pushing into their front. It seems a little strange that a unit that is holding its ground would allow another unit who is evidently performing a withdrawal maneuver to push it toward the enemy. If anything pressure to your front would push you back and pressure from behind would make you step forward.
I think the issue for me interpreting the interpenetration is that I feel that the act of interpenetration is moving fully through another unit, If at all possible. The rules allowing for that time when certain active units (the looser formations) run out of movement allowance and the other similar troop types can get out of their way. I am OK with that. It seems to me in the real world situation units that are moving through other units would continue moving until they were in open ground, so once (in this case) the S Unit started to move due to interpenetration, and they have no movement allowance to make them stop, they would interpenetrate then next unit, the rear FL, completely moving through them, whether 1 H or 5H. The “displacing movement” comes after the moving unit completes its movement.
In regards to the retreat:
5.11.2 b) says that if retreating any unit “can interpenetrate any unit(even if move distance remaining is not enough) if the interpenetration is allowed….5.11.1, or if the retreating unit is CL, T, or FL (non Impetuous).”
If interpenetration is moving through a unit, and can be done even if the move distance is not enough, than the FL unit would move completely through the other FL and not displace it.
In our playing we have not run into any of these situations yet. So it is good to air them out here .

I really struggled with the interpenetration rules in Basic Impetus 2 (see this thread https://impetus.darkbb.com/t1006-interpenetration-from-the-front ). The wording in 'full' Impetus 2 is slightly different, but seems to be aiming to the same effect. So here is my take on the meaning

Start with the requirement that 'When S, T, FL and CL are interpenetrated, these automatically allow the interpenetration, moving behind the interpenetrating Unit after movement is completed'. This is not qualified by 'may' or 'can' so is compulsory. You must place the interpenetrated S, T etc. behind the interpenetrating unit, then see what happens.

I agree it says later that that the interpenetrated unit 'can be forced to move forward' when there is interpenetration from the front, and I think you are reading this as something that is compulsory movement for any frontal interpenetration. I don't think that is right (I say that with some hesitancy). Instead, I see it as something that may ('can') happen if the circumstances are right. Specifically, if 'moving behind the interpenetrating unit' causes the unit to move forward, then so be it; don't be surprised by that outcome.

So in your specific example, Gaius, when FL1 'taps' the S, the S is moved back behind FL1. In doing so, it interpenetrates FL2, so FL2 is placed behind the S, since moving behind the interpenetrating unit is mandatory for FL when a FL unit is interpenetrated. Forward movement of FL2 doesn't occur because the compulsory 'moving behind' never triggers any forward movement. Effectively, the S forces space for itself between FL1 and FL2. This is different from Impetus 1, but makes a sort of sense.

I'm more than happy to be persuaded I'm wrong, and welcome your thoughts.

Note also (as in the Basic Impetus 2 thread), I think the paragraphs about forward and backward movement at a and b in 5.11.1 only apply when the interpenetrated unit is S, T, FL and CL. Otherwise, you get to the odd conclusion that S 'tapping' a large unit pike block of 3 bases forces the whole pike block to move (perhaps a significant distance) to accommodate the S.

After the difficulties we had with Basic Impetus 2, I wish the wording in Impetus 2 had been clearer.

RogerC

In your understanding RogerC when would a unit displace another to the front? I didn't pick that up in your commentary.

I agree with you that we are only dealing with S,T,FL and CL units in this discussion (and perhaps A). An S unit cannot displace FP for instance.

What one feels Scott is, respectfully, irrelevant. The only question on the table is what the rules intend. I agree with Roger C that clearer wording would have been helpful here.

Gaius

Apologies if I didn't say enough, Gaius; I'm usually prone to over-explaining rather than the reverse.

I think a unit of S etc. is displaced to its front when the interpenetrating unit is facing (generally) in the opposite direction to the interpenetrated unit (and its movement doesn't clear the interpenetrated unit). In such a case, moving the interpenetrated unit to the rear of the interpenetrating unit moves the interpenetrated unit forwards, since the rear of the interpenetrating unit is forward of the front of the interpenetrated unit. On this interpretation, such forward movement is likely to be rare.

As an example, imagine a unit of FL moving forward which encounters a unit of friendly S facing generally in the opposite direction and 'taps' it. The S must move to the back of the FL. and this has the effect of moving the S to its front (so forwards). That may be towards the enemy, depending on where the enemy is.

if you want a really complicated example, imagine the arrangement you described, Gaius, but with the S facing in the opposite direction to the 2 FL units. FL1 taps the S which must move behind FL1. In doing so, it moves to its front (so, forwards) but ths causes the S to interpenetrate FL2, which must move behind the S (so, forwards from the point of view of FL2). But that puts FL2 where FL1 is, with FL2 interpenetrating FL1. So FL1 must move behind FL2, again interpenetrating the S. So the S must move behind FL1 (which, again, is forwards for the S). The net result is that the S has moved all the way to the back of the 2 Fl units (moving forward from the point of view of the S), and FL1 and FL2 have swopped places.

Now I wouldn't be surprised if you said that was too complicated, but I don't think it is inconsistent with the wording of the rule, at least once you take 'moving behind the interpenetrating unit' as the mandatory step. As I said, I'm more than ready to be told I've got it wrong.

RogerC

Gaius Cassius wrote:The front FL wishes to end its movement partially on top of the S.

We play the interpenetration as if a unit has enough movement and room to clear the interpenetrated, then it has to do so. It cannot choose to stop in mid interpenetration.

Gaius Cassius wrote:Why is the Spanish player doing this? So that he can get maximum fire power against the enemy. He is rotating the three units through to get three shots at the enemy.

Even if the rules don't forbid interpenetration and shooting (perhaps they should!) we find difficult to imagine such maneuvers in reality. So the maximum we play is with one interpenetration and shooting. But this is our group view, of course.

We all agree that this is tricky and unclear rule to interpret.

Your scenario with the S turned around works fine. In that scenario the FL moves forward and taps the S from the S' front and it moves behind the FL (even though the S unit technically moves forward.) No problem there.

The S can also have its front tapped by the FL backing onto it (moving backwards or through a retreat or the FL being displaced backwards). In that case I don't see why the same principle in 5.11.1 doesn't come into effect. The rules state that when the interpenetrating units approaches from the front the unit being displaced is moved forward not backwards. I don't see any conditions to this principle. Orientation doesn't seem to be germaine to the question of which direction the unit displaces. In this case 5.11.1 a would be a modification to the broader principle of displacement noted above.

Of course 5.11.1 means whatever Lorenzo says it means so I make my claim conditionally.

As I said, Gaius, I treat the statement about forward movement as conditional, because of the 'can be forced'. On the other hand, I take the earlier reference to 'moving behind the interpenetrating unit' as mandatory.

So if S has it's front tapped by FL moving backwards, and the S is facing the same way as the FL, then the S is moved backwards to behind the FL. If the S was facing the opposite direction to the FL, then the S would move forward when it moves to behind the FL. In neither case does it end up in front of the FL.

I think you can make a coherent interpretation, in the way I've said, but I have no idea (even after the Basic Impetus 2 discussions) whether that is what Lorenzo wants it to mean.

You mentioned retreats, but that is another can of worms. What are we to make of 'it can interpenetrate any Unit (even if the movement distance remaining is not enough) if the interpenetration is allowed' in 5.11.2b? Does the bit in brackets mean that a retreating unit moves fully through any unit it is interpenetrating? If not, why would the bit in brackets be needed?

Maybe retreats are a separate discussion!

RogerC

I do see where you are coming from RogerC and it makes sense. You also have a good feel for Impetus so I take your comments seriously. If you are correct then it seems to me there is really no need for 5.11.1a. That is because the direction the unit causing the displacement is irrelevant. The unit displaced moves behind it. Simple. We don't need to know the movement direction of the displaced unit at all either. Forward or backwards, who cares? So why mention it. And the orientation of the displaced unit is irrelevant.

In 5.11.1a the direction of the displacing unit seems to determine where the displaced unit is moved to.

5.11.1b seems straightforward to me. If the unit causing displacement even partially overlaps another unit that unit displaces to the rear of the moving unit.

Thank you, Gaius, but I don't think I am any better at fathoming Lorenzo's mind than you are.

I agree that my interpretation doesn't really need 5.11.1a, but then 5.11.1c is a statement of the obvious for regular Impetus players, so who knows?

Maybe one day we'll find out what Lorenzo really intended. Meanwhile, we can try to do what seems to fit the wording of the rules, and enjoy our games.

RogerC

probably I missed something but on this point there is no difference between Impetus 1 and 2. S goes back once the first FL completes its movement. If there is no room, it finds it going back further (eg crossing the second FL)

Thanks Lorenzo. What is 5.11.1 a trying to say?

As an aside we find the ability to rotate several units a very powerful weapon in Impetus because the importance of taking a hit while disordered. I do think the faster movement and the shorter firing distances have slightly reduced its impact in Impetus 2.

Thank you, Lorenzo. I'd assumed the change in wording was intended to mean something different from Impetus 1.

RogerC