Legions interpenetrating other legions

One of the new features of the lists in Warbooks 1 and 2 is that legion infantry from the later Republican and early/mid Empire lists can interpenetrate each other. They are the only FP that can do this with other FP in the Impetus system. My question is the following.

If one legion routs through another legion behind it within 1U does the the legion routed through suffer automatic disorder and 1 VBU loss?

What a coincidence I was just about to put same query on forum.
As the rules are think it is clear they do trigger lose on unit routed through as there is know reference in the rules to the contrary. My query was should there be.
Our group is split I think they should cause loss as they are FP are now a rabble routing lost all formation.

I would think they would, since the rules say nothing to the contrary. That being said, a good case could be made that the unit routed through should suffer no VBU loss, because interpenetration is allowed and accounted for.

There really are no rules for FP interpenetrating FP so this is definitely a special case. This is one of the problems of providing special troop types through the lists.

I know i said would cause damage but this would reduce the effectiveness as would probably keep more distance between lines to avoid risk of taking losses

Gaius Cassius wrote:
If one legion routs through another legion behind it within 1U does the the legion routed through suffer automatic disorder and 1 VBU loss?  

Most definitely.

A routing legion is quite different to a well ordered legion with all it's moving parts and command structure still intact.

Doesn't actually say this anywhere I know but think it's one of those common sense occasions.

You are probably correct Tarty (along with ejc and kenntak) but most other troops that can interpenetrate and displace do not rout through each other with a penalty.  As ejc noted above, this makes the legions a bit less useful because of the risk of routing. Probably it is not cost effective to have a rear units of legions available so it won't matter too much in any event.

I do not see the problem here.

The rule 7.7.2 seems quite clear that a friendly unit behind a routed unit (within 1H) suffers disorder and a 1VBU loss. A list of exceptions is given, S, FL, T, CL etc. FP is not in the excepted list, and so causes disorder and loss.

Interpenetration is an entirely different matter and refers to a retreat from combat, not routing. So a legionary FP (with VBU greater than 0) can pass through a legionary FP behind it without being obstructed.

So, yes a legionary FP takes a disorder and 1VBU loss, if it is 1H behind a routed FP. Just as the rule says...

Am sure none of disagree with you. The question is should there be a rule to bring this situation into line with where troop types that when in good order can interpenetrate that when rout and become a rabble do not trigger losses on units within 1H to rear.

yes they cause the loss like all FP.

I have probably misunderstood the relatively new rule for legion infantry interpenetrating each other. The only useful need for interpenetration would be line relief and that is a little problematic under Impetus 2 given the possibility of rout. I suppose a lull in the battle line could make it a useful manoeuvre.
I miss the previous, more effective, line relief procedure because it just seemed right for Romans to deploy as single units with a safe space between them!
Although large Roman units are cheaper and resilient I do not like the look on the battlefield! A minor gripe, though, because Impetus is an excellent set of rules!