SEOUL, South Korea — Six decades after they returned to their homeland, traces of thousands of North Korean children orphaned by the Korean War linger for the elderly Europeans whose lives they briefly touched.

The scent of the trees they planted. The memories of their innocent faces. The Korean song they sang.

Some 5,000 orphans were sent to live in Poland, Romania, Bulgaria, Hungary, Czechoslovakia and East Germany — all communist allies — as part of Soviet-led projects to reconstruct war-ravaged North Korea.

The orphans studied in local schools and made local friends. Then, abruptly, they were called back to North Korea.

“We weren’t told — not at all — they just stopped coming to school,” said Halina Dobek, 87, who taught some of the orphans in Poland. “These children were leaving Poland with no enthusiasm.”

It’s a mostly forgotten slice of Cold War history, but a new documentary shines light on the lives of the orphans whose departure still weighs on the Europeans who knew them.

The film “Kim Il Sung’s Children” — referring to North Korea’s founder and wartime leader — will be released June 25, the 70th anniversary the Korean War’s start. The three-year conflict destroyed much of North and South Korea, killed more than 1 million people and orphaned an estimated 100,000 children.