I have spent 2 hours doing the same thing! And I have failed. :(
You father was at Nui Ba Den? Amazing! What did he tell you?
He was there several times to repair the "communications" equipment, which I suspect was navigational aids for aircraft interdicting the Ho Chi Minh Trail. They got hit a lot up there. Mr. Charles was not a good neighbor.
High ground is always key terrain. With quality optics and long range weapons you can play King of the Mountain over a big area.