The term "combat troops" is confusing to civilians (and some
military personnel too) because the term has been abused for so
long. All US Army personnel are combat troops with specialized
branches that specialize into specific combat jobs, formerly (which
is why they used to go to BOOT CAMP; formerly known as Basic Combat
Infantryman's Training) known as the combat arms branch: Armor
(tanks), Artillery (cannons), and the Infantry (formerly fighting
men/foot soldiers). During the late 1990 the US Army "may" have
added other branches to that specialized combat arms system. Rumor
control stated that the aviation branch was added to the combat
arms system.
The combat arms of the US Army are the conventional fighting
branches of the US Army (or was during the Viet War days).
US Combat troops, along with specialized troops were deployed to
SOUTH Vietnam in 1955. CONVENTIONAL forces (those combat arms men
previously discussed above were deployed in 1965).