vanguard
/ˈvan-ˌgärd/
noun
the forefront of an action or movement
the troops moving at the head of an army
idiom
in the position of the leaders of an action or movement in society, politics, art, etc.
They are at the vanguard of a revolution in medical research.
noun
the soldiers, ships, etc., that are at the front of a fighting force that is moving forward