[Griefbringer]

For further clarification, for an onboard unit to be able to fire indirectly, it needs to have a contact to it's own platoon HQ first. In the case of the Heart of Africa campaign, the mortars are unit C2 and their platoon HQ is C0.

If one is unwilling to rely on the vagaries of radio communication, then the surer way of establishing contact is having the platoon HQ in close physical proximity to the indirect fire unit - being within 5 hexes or so tends to provide very reliable line of communication to the platoon HQ.

However, in a platoon with mixed units - such as in the case of Heart of Africa campaign - this can cause a conflict of interests, since you want to have your platoon HQ both sitting back (to provide control for the mortars) and further front to provide leadership, fire support, spotting capability etc. to the rest of the platoon closer to the enemy. One way around this would be to attach the mortars to some other platoon that is more likely to be hanging back (such as the HQ A-platoon).

Ideally, the mortars should be organised as their own platoons, so the whole platoon can safely hang back and provide indirect fire.