November 14-18 1965, Battle of Ia Drang- the first battle between the PAVN or the NVA and the new in country US Army. Causalities: US -304 KIA-- PAVN dead estimated 1800 to 3000.
Lessons learned-the American Army figured that Air Mobility supported by artillery was a great tactic as the results were a 12-1 kill ratio. The Army conclusions sent innovation into hibernation at this point and no further thinking, other than attrition, was committed until General Creighton Williams Abrams Jr took over and changed from search and destroy tactics to clear and hold.
For the NVA, lessons learned were dubious at best and stupid at worse. Despite coming away with an awful casualty bill the NVA leadership, nevertheless, concluded that if you hugged the bear the American air and artillery advantage would be canceled. This was the thinking after taking a awful beating ratio of 12 NVA dead to one American. Solid thinking don't you think. Takes you right back to WWI.