Armored troops constitute a combat arm in name, although many have histories derived from cavalry units.
Only those Army Aviation units directly involved in armed combat such as air cavalry, attack helicopter, aerial rocket artillery, or assault helicopter operations were properly considered as "combat arms."
This meant that most Infantry officers were assigned to assault helicopter units while Armor and Field Artillery officers were most likely assigned to attack helicopter or aerial rocket artillery units, respectively.
Both Infantry and Armor branch commissioned officer aviators were assigned to Air Cavalry units, as these squadrons consisted of troops containing a mix of attack helicopter, aerial reconnaissance, and "aero-rifle" platoons.
Until 2004, Army warrant officer (WO) aviators were appointed/commissioned into the Warrant Officer Corps in the Army "at large" and in a WO MOS in which they were qualified depending upon the aircraft category (i.e., fixed-wing or rotary-wing) and the mission/type/model(s) of aircraft in which they were rated.
From 1952 until 1987, Army Special Forces (SF) were essentially a subset of the Infantry Branch with most of its officers and many of its enlisted soldiers coming from traditional infantry MOS backgrounds; however, in 1987 owing to a heightened emphasis on special operations, SF was established as a combat arms basic branch.