Etymology
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close quarters (n.)

1722, originally nautical, also close-fights, "bulkheads fore and aft for men to stand behind in close engagements to fire on the enemy," it reflects the confusion of close (v.) and close (adj.); "now understood of proximity, but orig. 'closed' space on ship-board where last stand could be made against boarders" [Weekley]. Compare also closed-minded (1880s), a variant of close-minded, as if "shut" rather than "tight," also closed-fisted, occasional variant of close-fisted "stingy."

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civil service (n.)

"the executive branch of the public service," as distinguished from the military, naval, legislative, or judicial, 1765, originally in reference to non-military staff of the East India Company, from civil in the sense "not military." Civil servant is from 1792.

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Agent Orange (n.)
powerful defoliant used by U.S. military in the Vietnam War, reported to have been used from 1961; so called from the color strip on the side of the container, which distinguished it from Agent Blue, Agent White, etc., other herbicides used by the U.S. military; see agent (n.). Banned from April 1970.
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plain clothes (n.)

"ordinary dress of civil life" (as opposed to military uniform), 1822; in reference to police detectives, it is attested from 1842. Also plainclothes.

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point man (n.)

"one who leads a military patrol in formation in a jungle, etc.," 1944, said to be from point (n.) in military sense of "small leading party of an advance guard" (1580s) + man (n.). A more literal sense also is possible. Point (n.) in U.S. also meant "position at the front of a herd of cattle," and pointman in this sense is attested by 1903.

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Iron Cross 
from German eiserne kreuz, instituted 1813 by Frederick Wilhelm III of Prussia, originally for distinguished military service in the wars against Napoleon.
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left wing (n.)
also (as an adjective) left-wing, 1871 in the political sense (1530s in a military formation sense), from left (adj.) + wing (n.). Related: Left-winger.
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Silver Star 
U.S. military decoration awarded for gallantry in action, originally (1918) a small badge worn on the ribbon of a campaign medal; as a distinct medal, it was established Aug. 8, 1932.
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life of Riley (n.)

"life at ease," by 1902 (as Reilly), popularized in U.S. during World War I; it seems to have been military slang initially, sometimes said to trace to various songs but none of that title has been found.

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rank and file (n.)

1590s, in reference to the horizontal and vertical lines of soldiers marching in formation, from rank (n.) in the military sense of "number of soldiers drawn up in a line abreast" (1570s) + file (n.1). Thence generalized to "common soldiers" (1796) and "common people, general body" of any group (1860).

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