point man

noun2

1. •
   In combat, the soldier who takes point; the soldier who assumes the first and most exposed position in a combat military formation; the lead soldier/unit advancing through hostile or unsecured territory.

   • The point man is the only one besides the Shooter who could verify the kill shots firsthand, and he did just that to another SEAL I spoke with. — 2013
2. •
   A most trusted assistant or associate; the person upon whom one would most rely.

   • McCarthy made a name for himself as a point man for a far right-wing current that attacked the Truman administration for the "loss" of China. — 2005