vanguard

noun

1. The leading units at the front of an army or fleet.

   “They ſay, that the King diuided his Armie into three Battailes; whereof the Vant-guard onely well ſtrengthened with wings, came to fight.”

2. (broadly)The person(s) at the forefront of any group or movement.

   “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.”

   “[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.”

   “The outsiders are looking more like insiders, the vanguard of a cultural and political shift that could be far more profound than in his first presidency.”