Definition from Wiktionary, the free dictionary
vanguard (plural vanguards)
- The leading units at the front of an army or fleet.
- (by extension) The person(s) at the forefront of any group or movement.
1922, Ben Travers, chapter 4, A Cuckoo in the Nest:
- By some paradoxical evolution rancour and intolerance have been established in the vanguard of primitive Christianity. Mrs. Spoker, in common with many of the stricter disciples of righteousness, was as inclement in demeanour as she was cadaverous in aspect.
2014 November 17, Roger Cohen, “The horror! The horror! The trauma of ISIS [print version: International New York Times, 18 November 2014, p. 9]”, The New York Times:
- [O]ne minute this "Jihadi John" was struggling to get by, and get accepted, in drizzly England, unemployed with a mortgage to pay and a chip on his shoulder, and the next he stands in brilliant Levantine sunlight, where everything is clear and etched, at the vanguard of some Sunni Risorgimento intent on subjecting the world to its murderous brand of Wahhabi Islam.
leading units of an army
forefront of any group or movement