To name a few important items:
1. M41 Walker Bulldog light tanks for their armored forces.
2. A1 Skyraiders for their air force.
3. M16 assault rifles for their infantrymen.
Note: Number 3 is important because since 1955 the South Viet infantryman had been armed with US WWII rifles & machine guns. (# 2) Although the A1 Skyraider was a "WWII designed" airplane (propeller driven) it didn't fight in WWII; its first war was in Korea...and the A1 (nicknamed the SPAD and Sandy) was probably the best ground attack plane in the war because it carried more bombs and bullets and stuck around the battlefield longer than any other US warplane. The A1 had to be replaced because they were being used up and no more were being built. Todays famous A-10 Warthog (jet) is the equivalent of the A1 Skyraider...in performance, mission, durability, reliability, firepower, and protection.
The Korean war
The US never invaded Vietnam.
South Vietnam was considered an ally of the US.
US Military personnel were in Vietnam from 1955 thru 1975.
See: Vietnam
Vietnam
We were at war with Vietnam because they disagreed with us about something.
The French were fighting in Vietnam in 1950 not the US.
The US was concerned about the development of Communism in Vietnam
The fear of being invaded was not a justification for the increase in US involvement in Vietnam. The US withdrew from Vietnam in 1975.
The US wanted N. Vietnam to stop fighting in S. Vietnam.
Yes. Before the US committed to the Vietnam War, many Americans had not even heard of Vietnam.