1. under arms - Adjective
2. under arms - Adverb
armed and prepared for fighting
Source: WordNetThere are 40,000,000 men under arms in the world today, and our statesmen and diplomats have the temerity to say that war is not in the making. Hell's bells! Are these 40,000,000 men being trained to be dancers? Smedley Butler
Who on earth could blame them? Ah, no wonder the men of Troy and Argives under arms have suffered years of agony all for her, for such a woman. Beauty, terrible beauty! A deathless goddess-so she strikes our eyes! Homer
Visit the Navy-Yard, and behold a marine, such a man as an American government can make, or such as it can make a man with its black arts -- a mere shadow and reminiscence of humanity, a man laid out alive and standing, and already, as one may say, buried under arms with funeral accompaniments. Henry David Thoreau
About 250,000 men served as regulars or as militiamen for the Revolutionary cause in the eight years of the war, but there were never more than 90,000 men under arms at one time. Source: Internet
By May, Jefferson Davis was pushing for 100,000 men under arms for one year or the duration, and that was answered in kind by the U.S. Congress. Source: Internet
Charged for two counts of robbery under arms is Ronald Armstrong of Parika, East Bank Essequibo (EBE). Source: Internet