In the moutainous regions of northern South Vietnam--the I Corps and II Corps tactical areas--lived the various Montagnard tribes.  Some say there were as many as 30-35 different tribes, each with their own language, culture, customs and religion.  I had experience with four tribes--Hre (Gia Vuc), Rhade and Koho (II Corps), and Bru (Lang Vei).  Tribes typically occupied a specific geographical area, and tended to remain in that area.  Each tribe's dialect and customs could be very different from an adjacent tribe.

At Gia Vuc, the many scattered settlements of the Hre had in common their family orientation, their subsistance on crop-based agriculture, and if prosperous enough, on poulty, swine and water buffalo. It was a prosperous family, indeed, that could afford a water buffalo living beneath their elevated bamboo house!

It may have been the rice cycle that was one of the single most dominant events in the Montagnard's life.  Indeed, life depended on it.   Despite USAID efforts to introduce rice capable of two yields annually, the Rhe maintained their single annual rice crop cycle.

The cycle began with planting and ended with cutting, hulling and storing in isolated storage houses back in the paddies.  The Viet Cong, and the NVA, knowing the cycle, always came after hulling.  The isolated storage houses made it almost impossible to prevent nightly foraging and looting at this important time of year.
The NVA, and the VC, would often attempt to use "psy-war"efforts at this time of year, in order to try and intimidate, and curtail, the camp's longer-range operations, and shorter-range nightly ambushes.

If the psy-ops weren' t effective in curtailing the camp's operations, the VC and NVA would often attack the camps, to attempt greater unrestricted access to the stored rice.  Using Montagnards forced to be porters, large hauls were often looted from the many dispersed storage areas. These efforts were never totally stopped, as far as I know. There were too many dispersed rice storage areas, and simply not enough ambushes that could be put in the field. 

To my knowledge, the Hre never changed their custom of remote storage, nor their single annual planting and harvest cycle.  Tradition and culture are not easily changed!