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vanguard

noun

the foremost division or the front part of an army; advance guard; van.
the forefront in any movement, field, activity, or the like.
the leaders of any intellectual or political movement.
(initial capital letter) Rocketry. a U.S. three-stage, satellite-launching rocket, the first two stages powered by liquid-propellant engines and the third by a solid-propellant engine.

noun

the leading division or units of a military force
the leading position in any movement or field, or the people who occupy such a positionthe vanguard of modern literature

mid-15c., vaunt garde, from Middle French avant-garde, from avant “in front” (see avant) + garde “guard” (see guard (n.)). Communist revolutionary sense is recorded from 1928.