81 mm Mortar crewman setting up the mortar.  Excellent illustration of firebase construction.

The mortars are for close in support and illumination at night.  Many firebases have been saved from total annihilation due to the valor of the mortar crews and the artillery crews firing direct fire.  Fire base construction lasts throughout the life of the firebase, the rifle companies do not look forward to the initial construction, it is almost more work than humping the boonies.