 Specialist 5 Johnson, a tank driver with Company B, was a member of a reaction force moving to aid other elements of his platoon, which was in heavy contact with a battalion size North Vietnamese force.Specialist Johnson's tank, upon reaching the point of contact, threw a track and became immobilized.Realizing that he could do no more as a driver, he climbed out of the vehicle, armed only with a .45 caliber pistol.