a question came up today in a game i was playing. i had two units of marines (both with counterassault) in cover. my friend's two units of marines charged my two units, and the entirety of the charge was blocked on both sides by a pair of land raiders. his assault moves were not split, so these were effectively two separate combats.
after contacting my units and getting as many of his models into contact with mine as possible, i still had several unengaged models in both squads. counterassault ability happens.
1) do i have to roll a difficult terrain test for my counterassaulting models if they move through cover? (the rulebook says to treat this move like an assault move with a couple exceptions)
2) do the counterassaulting models strike last against my friend's models that were in cover at the time of the counterassault ability going off?
3) does the fact that a combat already exists, and my models are charging into it, negate the ability of my friend's models to strike at initiative 10 before my counterassaulting models?
4) can i split my 'counterassault' by charging multiple units?
5) ...and how exactly am i supposed to view the counterassault rule? is it even supposed to be an 'assault move' or is it more of a pre-combat pile-in move that ignores models and terrain?