Under arms describes a state of military readiness (actual or ceremonial). Typically, troops are considered "under arms" when they are in
uniform
A uniform is a variety of clothing worn by members of an organization while participating in that organization's activity. Modern uniforms are most often worn by armed forces and paramilitary organizations such as police, emergency services, se ...
, on duty, and carrying a weapon (
rifle
A rifle is a long-barreled firearm designed for accurate shooting, with a barrel that has a helical pattern of grooves (rifling) cut into the bore wall. In keeping with their focus on accuracy, rifles are typically designed to be held with b ...
,
side-arm, or
sword
A sword is an edged, bladed weapon intended for manual cutting or thrusting. Its blade, longer than a knife or dagger, is attached to a hilt and can be straight or curved. A thrusting sword tends to have a straighter blade with a pointed ti ...
), as opposed to being in uniform, on duty, but not carrying a weapon.
Soldiers not actually carrying a weapon but wearing a service belt or web gear associated with carrying weapons may be considered to be symbolically "under arms".
Soldiers normally remove headgear while indoors; however, soldiers who are under arms normally wear their headgear indoors, with a few exceptions.
References
Military organization
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