Forward Observation Officer
|Fuck ... the FOO just blew up my lunch!|
His job is to co-ordinate ALL the Joint Fires in a fire plan to support an attack, defence or whatever. So whatever the GPMG /MFC troopie may tell you, all his stuff belongs to the FOO, alongside mortars, EW, AH, CAS etc etc.
The actual work of adjusting artillery fire is usually done by the OPAck as the FOO will be away somewhere explaining to a grunt Major why it is that the Major's plan is bollocks and nothing should be done until the big guns are ready to do their battle-winning stuff.
Also known as a FST Commander.
Note: The called in fire will still be short, left, right, impacting your portaloo but it will always be someone else's fault.