The official color of the warrant officer corps is brown, as warrant officers in the mine planter service wore simple bands of brown cloth on their uniform sleeves as their insignia of rank. Warrant officers served in four positions aboard the vessels: masters, mates, chief engineers and assistant engineers. Masters wore four bands. Deck officers also wore an embroidered brown fouled anchor above the braid, while engineer officers wore an embroidered brown three-bladed propeller in a similar position.
The Act of 1920 expanded use of warrant officers, authorizing appointment of warrant officers in clerical, administrative, and band leading activities. This Act authorized 1,120 warrant officers, provided for appointments in the Army-at-large rather than in specific branches and established warrant officer assignments in various headquarters and tactical units. Perhaps the most significant motive for the expansion was
". . . a desire to reward enlisted men of long service and also to reward former commissioned officers of World War I who lacked either the educational or other eligibility requirements necessary for continuance in the commissioned status." In 1921, warrant officers were excluded from performance of summary court officer, defense counsel, officer of the day, and assistant adjutant because enlisted personnel were prohibited from performing those same duties. During this time, only one pay grade existed except in the army mine planter service.
Warrant officers of the tank corps first wore the distinctive insignia approved on 12 May 1921. It consists of an eagle rising with wings displayed, standing on two arrows and enclosed in a wreath. It was adapted from the great seal of the United States, with the arrows symbolizing the military arts and science.
Eagle Rising - "An eagle rising with wings displayed standing on a bundle of two arrows, all enclosed in a wreath.“
In 1922, the warrant officer strength authorization dropped from 1,120 to 600, exclusive of the number of Army mine planter service warrant officers and Army bandmasters. Consequently, there were no warrant officer appointments other than bandmasters and Army mine planter service personnel between 1922 and 1935. Laws subsequent to 1922 authorized the appointment of additional classes of personnel with certain qualifications, above the 600 authorizations.
In 1936, the Army held competitive examinations to replenish lists of eligibles for Regular Army appointment. The Army appointed warrant officers against vacancies from this 1936 list until the beginning of World War II.
In 1939, warrant officers who were qualified as pilots were declared eligible for appointments as air corps lieutenants in the Regular Army.
In 1940, warrant officers began serving as disbursing agents.