How were helicopters used in the Vietnam War?

Helicopter Pilots landed troops onto foreign soil, several stating they could smell the death in the air, also they evacuated the wounded. Firing cover for the troops, The door gunners &Pilots had a short life-span. The Pilots did use loud speakers on their choppers to put the "fear" of their music into the north(ex."Paint It Black") VC. And each time they landed in a "Hot" LZ meant enemy fire each time. The Choppers were invaluable in Viet Nam. RIP SSgt. Roy D. Nelson, 173rd AB & 82nd "Blackhorse" Armoured Calvary.1967-1971