Slitherine

Units A declares a charge on Unit C, impetuous unit B is directly behind A but in charge range of unit C.

Does B test to charge impetuously and if it does so does it preempt unit A's charge on C?

What the sequence of charges and impetuous charges and their interaction?

Does B test to charge impetuously and if it does so does it preempt unit A's charge on C?

From what I can tell unit B has to test to not charge. C is in range and B can see it so to keep them in place they would have to pass a CMT. Page 20 sequence says active player may charge any units in any order of their choosing, so A can charge first then if B has failed the stand still CMT they go whenever you want, so long as they have charged during the turn.

What the sequence of charges and impetuous charges and their interaction?

As stated above, page 20 sequence says you resolve charges in any order you like, you just have to designate the charging unit and the target unit. Target of a charge will always react the same whether it is impetuous or normal charge. A non-charging unit that the impetuous unit charges through has to take a cohesion test for being burst through basically.

My advice to you is don't take impetuous troops or move them after any chargers out front have moved or just keep everyone out of their way.

If A charges they is no way for B to make a legal charge in this case. If A charges and contacts C, B cannot contact C as A is in the way. IF B charges through A then A cannot make legal charge contact. one must preempt the other..

I have to agree with you.
However it is a case of the turn sequence not agreeing with whats going on table. Similar problem you find with intercepts, follow turn sequence you declare charge on wavering troops, they test fail and rout. However if you intercept the chargers then they don't take the test so go back to their starting point and return from broke to wavering in their previous formation and facing. I think the turn sequence needs to be revisited and revised with some sub phases being added in or something.

Making impetuous charge first then other charges would perhaps clear this up.

However in this case page 28 bullet 11 might hold the answer. Basically it states that they must pass a CMT if they could contact an enemy unit.... This seems to be a key point in your example, unit A has declared a charge, this means B can not contact that enemy unit, so logically it negates their forced charge. They can't contact it so they don't have to make the charge even if they wanted to.

Now if there was another enemy unit within reach then I would suggest that enemy unit would become their new primary target and could force the Impetuous charge.

Since it is your choice as the phasing player to make your charge moves in any order you wish, you can still declare a charge with A and only if A does not charge, they are disordered and fail the CMT, would B then be forced to charge that unit and burst through A.

However in this case page 28 bullet 11 might hold the answer. Basically it states that they must pass a CMT if they could contact an enemy unit.... This seems to be a key point in your example, unit A has declared a charge, this means B can not contact that enemy unit, so logically it negates their forced charge. They can't contact it so they don't have to make the charge even if they wanted to.

Now if there was another enemy unit within reach then I would suggest that enemy unit would become their new primary target and could force the Impetuous charge.

This is correct.
If the first unit declares a charge, the 2nd (impetuous) unit only tests is it could still make contact with the same or different enemy without passing through another charging unit.
If you have 2 impetuous units you should decide which order to test them. If the first one fails its test and blocks the route of the 2nd unit, then the 2nd unit need not test.