Operation thumb|right|Sơn Mỹ operations, 16 March 1968 Charlie Company, 1st Battalion, 20th Infantry Regiment, 11th Brigade, 23rd Infantry Division, arrived in South Vietnam in December 1967. Though their first three months in Vietnam passed without any direct contact with People's Army of Vietnam or Viet Cong (VC) forces, by mid-March the company had suffered 28 casualties involving mines or booby-traps.
Operation thumb|right|Sơn Mỹ operations, 16 March 1968 Charlie Company, 1st Battalion, 20th Infantry Regiment, 11th Brigade, 23rd Infantry Division, arrived in South Vietnam in December 1967. Though their first three months in Vietnam passed without any direct contact with People's Army of Vietnam or Viet Cong (VC) forces, by mid-March the company had suffered 28 casualties involving mines or booby-traps.