Vanguard (military tactics)
WordNet
noun
(1) The position of greatest importance or advancement; the leading position in any movement or field
"The Cotswolds were once at the forefront of woollen manufacturing in England"
"The idea of motion was always to the forefront of his mind and central to his philosophy"
(2) The leading units moving at the head of an army
(3) Any creative group active in the innovation and application of new concepts and techniques in a given field (especially in the arts)