The Vietnam War ranks among the 20th century’s most momentous and horrendous calamities. The United States, in a desperate bid to roll back the spread of communism and to curtail the unification of a divided Vietnam, let loose the full might of its unparalleled arsenal on a penurious peasant society. The record of this carnage is extensively documented. Much less is known about South Korean involvement in this disaster. This article provides an in-depth analysis of South Korean war crimes, explains why they still matter and explores how their legacy casts a stubborn shadow over Vietnamese-South Korean relations today.