advance troops; vanguard; leading unit
Military term for the foremost unit in a formation or operation. Also used figuratively for the leading group in any organized effort.
See also: 先遣部隊
The advance troops charged into the enemy position.
He played an active role as the vanguard of the project.
先遣部隊 is a unit sent ahead for reconnaissance or preparation, while 先頭部隊 is the leading element in an actual advance or attack.
Compound of 先頭 (sentō, 'head, lead') and 部隊 (butai, 'unit, corps').