Analysis of information sources in references of the Wikipedia article "Under arms" in English language version.
Officers and enlisted men under arms uncover only when ... Seated as a member of (or in attendance on) a court or board [or] Entering places of divine worship [or] In attendance at an official reception.
The leather service belt is the standard sword belt for officers and may be issued to SNCOs and NCOs for ceremonies, parades, honor guards, and reviews when the sword is prescribed, and upon other occasions when an individual is actually or symbolically 'under arms.'
[Headgear s]hould not be worn indoors or in no-cover areas unless under arms
[Headgear s]hould not be worn indoors or in no-cover areas unless under arms