As SG says, in E:A, hits (from shooting and assault) are allocated 'front-to-back' relative to the formation causing them. In this case, anything that is in B-B with an enemy unit is automatically 'closest' to the enemy, so get hits allocated first. However where there are several units equally close, the defender choses the order of allocating the hits (so he can try to avoid allocating hits to a character).
Note that, apart from the WE section quoted by Mephiston, normally all assault hits are pooled together by type and then allocated front-to-back. (see 1.12.5, which refers back to 1.9.6), so in summary the full assault sequence is:-
- Roll dice for all unit involved in the assault (units in B-B using their CC value; units within 15cm and LoS using their FF value)
- Group all 'normal' hits together, make a second pile of all 'MW' hits, and a third of all 'TK' hits
- Allocate all 'normal' hits**** front-to-back and resolve them.
- Then allocate all 'MW' hits front-to-back and resolve them
- Finally allocate and resolve all 'TK' hits front-to-back
Note
**** The allocation of shooting hits is slightly different in that 'normal'
shooting splits hits between AT and AP targets, while
assault hits ignore this distinction.