Question about reactions

Hi,

Played a couple of Impetus 2nd games so far, still trying to set my mind on the way the new rules work. During yesterday's game there was one situation that arose question on how reactions work.

Basically my understanding is that for single action can only be one reaction.
So you can either react with single unit, or single group of units (as long as they are all targets of action). If you choose a group reaction, you have to choose a single reaction for the whole group (so for example you cannot close ranks with some units and use defensive fire with other units). If the group is fragmented, you need to roll for reactions separately for each unit, if not - you roll once for whole group. In addition to that - you can choose to evade with whatever unit/units are the target of the action.

So for example, given that the target of my single charge was a line of Late Roman Legionaries (4 or 5 units in total) and a single unit of Cataphracts, my opponent could react with EITHER Cataphracts or with any SINGLE Legionary unit or with a GROUP composed of any number of target Legionary units ?

I believe this case is pretty clear if you loot at an example given in the book, but wanted to double check

Thanks

as you say. You can make only one reaction (or as an alternative 1 evasion) and you can do with the single Unit (the "targetted" Unit). You can also react with the Group. In this case, if the Group is Fragmented you can declare a single reaction so all Units can try to react but as they must roll separately some will do and probably some not.

If a group reacts with defensive fire, 6.7 states that the test (and fire) is unit by unit. It behaves like a fragmented group, correct?

Such a group is also limited in number to the melee main and support units.

Why would it behave like a fragmented group? The test is done unit by unit.

Exactly. In a fragmented group each unit tests separately. Otherwise the group tests only once.

A fragmented group tests as a group for movement purposes. What else is it used for in Impetus 2?

Gaius, is this a question?

Here is a follow up question.

Does the limitation of only 1 reaction apply to ZOC reactions as well? For example, assume an enemy group moves through the ZOC of two friendly units that are not in a group, without any possibility of charging those friendly units. This would trigger an opportunity charge reaction. Would both those units be able to charge the enemy group (units can always react to a ZOC violation 4.1.4), or would only one of the friendly units be able to react (5.2 - a group movement generates a single reaction)?

Does anybody have any comments on the above question?

Units can react as many times as their ZOC is violated.
In your example I think both can react if applicable. Both could shoot but only the first could charge.