Why can't my FO order his mortars to fire

[Artofwar]

Ok I have an AO and then I have an infantry squad company whatever it is .. I choose it from the Battle set up it has an F0(the F0 here is not a forward observer but a German uber LT he is head of the platoon of F's) , F1, F2,F3, and F4 F1 -F3 are Infantry grunts under the FO Lt. ... F4 is the mortar platoon section whatever .. anyway, I figure the F4 comes under the F0 so Y can't the F0 tell my F4 mortar to fire at something. AND Y can't my F4 mortars fire at what they can see.

I press B and it only allows my AO to direct mortar fire and the AO is way back

I read the Guide but I'm to dense also it seems from the forums I was suppose to by about 25 FO... Forward Observers...