Gooooooood morning y’all. Robin Williams improvized for 12 hours and they took bits to put in the movie. Helpful to appreciate the jokes:
DMZ: Demilitarized Zone, https://en.wikipedia.org/wiki/Vietnamese_Demilitarized_Zone
Da Nang Air Base was used as a primary entry point for American service members flying into Vietnam fighting in the Vietnam War https://en.wikipedia.org/wiki/Da_Nang_Air_Base
Hanoi Hannah was a Vietnamese radio personality best known for her work during the Vietnam War, when she made English-language broadcasts for North Vietnam directed at United States troops, https://en.wikipedia.org/wiki/Hanoi_Hannah
The Ho Chi Minh trail was a gigantic network to supply the communist resistance in South-Vietnam from North-Vietnam. The US tried to disrupt the flow of supplies but never succeeded https://en.wikipedia.org/wiki/Ho_Chi_Minh_trail
The character played by Robin has just come over to Vietnam from Crete
Police action >>>> officially the war was undeclared
RVN >>> The army of South-Vietnam until the fall of Saigon in 1975 https://en.wikipedia.org/wiki/Army_of_the_Republic_of_Vietnam