Korea’s participation in the Vietnam War was a key element of Lyndon Johnson’s Vietnam strategy and a response to the shifting sands of the global Cold War. President Johnson wanted them because he was keen on increasing the number of ground troops in Vietnam without having to confront an increasingly skeptical American public. The Koreans carried American weapons, but their actions were largely ignored by the American press — which is just how Washington wanted it.

South Korea had its own reasons to be there. It was alarmed by the United States’ plan to move two of its military divisions stationed in South Korea to Vietnam and what that would mean for its security in relation to North Korea. And so it rallied to the cause of fighting communism abroad, what one official called “the holy war in defense of the free world.” South Korea also wanted to turn its Vietnam experience into a springboard for its own economic development, remembering Japan’s economic recovery after the destruction of World War II and against the backdrop of the destruction of the Korean War, from 1950 to 1953.

South Korean soldiers likewise saw an opportunity. On the one hand, they could pay back what they honestly believed was a debt for American sacrifices in Korea; on the other hand, they thought the money they earned from combat pay could give their families a leg up in a country that was still mired in poverty.

Memories of the Korean War influenced the evolution of the Vietnam War in other ways. Haunted by China’s intervention in Korea in October 1950, the United States never considered the possibility of pushing the Communist North Vietnam back from the 17th Parallel, which divided the two countries. South Korea’s top brass and politicians bragged about the efficacy of their armies in counterinsurgency warfare resulting from the Korean War experience — something the American Army, experienced in conventional warfare, was allegedly less familiar with.

At the same time, North Korea made a series of provocations against its southern enemy, in part to divert American attention away from Vietnam. And it was during the 1960s, with America apparently busy elsewhere, that Pyongyang began its so-called parallel politics, aimed at pursuing both economic development and military advancement — a policy that continues today.