spearhead

Short definition from Wiktionary

Noun

1. 1
   The pointed head, or end, of a spear.
2. 2
   One who leads or initiates an activity (such as an attack or a campaign).
3. 3
   The leading military unit in an attack.
4. 4
   A player who initiates attacking moves.

Verb

1. 1
   To drive or campaign ardently for, as an effort, project, etc.; to direct.