First Lieutenant Thacker's official Medal of Honor citation reads: For conspicuous gallantry and intrepidity in action at the risk of his life above and beyond the call of duty.

1st Lt. Thacker, Field Artillery, Battery A, distinguished himself while serving as the team leader of an Integrated Observation System collocated with elements of 2 Army of the Republic of Vietnam units at Firebase 6.

A numerically superior North Vietnamese Army force launched a well-planned, dawn attack on the small, isolated, hilltop fire base.

Employing rockets, grenades, flame-throwers, and automatic weapons, the enemy forces penetrated the perimeter defenses and engaged the defenders in hand-to-hand combat.

He occupied a dangerously exposed observation position for a period of 4 hours while directing friendly air strikes and artillery fire against the assaulting enemy forces.