2 soldiers obseved object while on guard duty

I and another soldier were assigned 4 hour guard duty at transportation depot.  Depot was fenced (10'chain link with wire), rectangle in shape, with area lights at 4 corners and gate. Depot was mostly dark inside fence.  
We walked perimeter of fence, met at rear and smoked and returned to front.  We were armed with M-14 rifle and 10 rounds apiece.  
Spotted object descending very slow, stop and hover about 500 feet away and 300 feet high.  It came in against slight breeze.  We stayed together until object left.  Object left same in same direction it came in.  We continued walking perimeter and observed a vehicle with emergency lights blinking.  It was dark in this area and vehicle was dark before object appeared.  
We loaded our weapons and continued guard duty.  We did not report the sighting for fear of ridicule, only the flashing vehicle.  Object had 6 lights across bottom.  6 inch diameter at arm's length, with no sound.
Source of report indicates that the date is approximate.  PD