Even language carried over from one war to the other. “Gooks,” the derogatory term for Koreans used by some Americans in the Korean conflict, was now used to refer to all Vietnamese — as well as the Koreans who had come to help the Americans to fight. Indeed, for all their idealism about fighting alongside Americans, the racial reality quickly became a source of profound disappointment and disillusionment with American power.

Which isn’t to say they shirked their duty; in fact, South Korean troops quickly earned a reputation as a ferocious fighting force — and found themselves, like Americans, mired in a people’s war with an entrenched and motivated enemy. The result was predictable, but no less tragic.

On Feb. 25, 1968, South Korean soldiers rounded up and killed 135 unarmed residents of Ha My. A month later, a similar tragedy ensued in the neighboring province of Quang Ngai, later known to the international community as the My Lai massacre. These two incidents were only a small part of the gigantic human catastrophe, part of a systematic assault against civilians by ground troops that was sweeping across central Vietnam in 1967.

Indeed, the massacres in Ha My and My Lai were closely connected. Ha My took place shortly after the Fifth United States Marine Regiment had handed security responsibility for the area to its Korean colleagues. My Lai took place soon after American troops took over control of the area from the Second Brigade of the South Korean Marines.

This wasn’t a coincidence. The tragedies arose out of the geopolitics of the Cold War, in which states on either side of the bipolar showdown aligned themselves in conflicts far from their home turf. The United States and South Korea were allied in the name of a crusade against communism, but South Korea was always the junior partner in America’s network — which explains why it did the dreadful work of village pacification, away from the attention from the international community and, perhaps more important, from the American public.

On June 6, 2017, South Korea’s Memorial Day, the newly elected president, Moon Jae-in, addressed the country’s Vietnam War veterans, declaring that Korea’s economic takeoff was indebted to their sacrifice in Vietnam. A few days later, I received an email from a Vietnamese journalist who asked how the history of Korea’s Vietnam War should be told in Vietnam and Korea. Shortly thereafter, another email came in, from a South Korean NGO that is active in reconciliation efforts regarding the Vietnam War violence between the two societies.

They all asked the same question, and I didn’t know how to respond. Vietnam and South Korea are now the closest allies in East Asia, but officially, they’d rather not discuss the war. The Vietnamese government wants to look to the future rather than reflect on its recent past; the South Korean government is focused on unresolved issues with Japan dating from World War II.

One thing is clear, however: For the people of Ha My, that tragic past is far from a thing of the past. And it is they who commemorate, today as in countless days in the past, the living traces of Korea’s Vietnam War as they set out at dusk to offer incense and flowers to the ghost of a non-Vietnamese-looking Asian soldier dressed in an American uniform.