if one unit fires at another, the firing unit has a clear target, unit A fires at unit B. there is no argument there. Split fire specifies that a model with split fire picks a different target to the unit. 'the unit' has fired at a target, the split fire model has fired at something else. It doesn't matter how many models are in the unit, a two model unit still has a target for 'the unit' and a target for the model with split fire. Charistoph is correct up to that point. as to which can be assaulted, I will have to get home and read the assault rules unless someone posts them here. if you consider why the rule exists from a fluff perspective, one unit has focussed its' attention on one enemy unit, and is not as aware of other enemy units and so cannot charge them. the model with split fire is able to focus his own attention separately to the rest of his comrades. the rest of the unit doesn't know what he is looking at, and carries on focussing on their chosen target, and so charges them.