2nd battalion, 3rd Marines at Kon Tum was the battalion Marshall Murdock supposedly served in during 1966.
The novelization of the film by David Morrell provides a greater explanation on the 2nd battalion, 3rd Marines at Kon Tum and why Rambo knows about them.
Rambo: First Blood Part IIEdit
Murdock thanks John Rambo for his service, claiming that he served in the 2nd battalion, 3rd Marines at Kon Tum in 1966.
Later in the film, Rambo asserts that the 2nd battalion, 3rd Marines was at Kud Sank, not Kon Tum as Murdock claimed. Colonel Sam Trautman suggests that he may have just misspoke, but Rambo says that you don't mix up such an important and traumatic part in your life. He then tells Trautman that he is the only one he trusts.