 Fire Support Base Giraffe was subsequently established with the new 105 @-@ millimetre ( 4 @.@ 1 in ) M2A2 Howitzers of 106th Field Battery and 81 @-@ millimetre ( 3 @.@ 2 in ) mortars from Mortar Platoon , 7 RAR providing indirect fire support , while elements of the Australian Reinforcement Holding Unit provided protection . Further support was provide by 155 @-@ millimetre ( 6 @.@ 1 in ) M109 self @-@ propelled medium guns from the US 2 / 35th Artillery Regiment , while American 8 @-@ inch ( 200 mm ) and 175 @-@ millimetre ( 6 @.@ 9 in ) heavy artillery were also available if required . Meanwhile , elements of 1st Field Squadron , Royal Australian Engineers had been tasked with clearing Route 2 of vegetation and rubber north of Nui Dat and D Company , 2 RAR was attached for the operation , providing security for the engineers and additional protection to the fire support base in conjunction with a troop of M113 armoured personnel carriers from A Squadron , 3rd Cavalry Regiment which would support the infantry during the day . 
