...So far, Jin’s team has identified 70 U.S. soldiers from the bones returned by North Korea in 2018 — a group the accounting agency calls “K55” in reference to the number of cases they were sent in. It also distinguishes them from “K208,” a large set of remains shipped from North Korea in the early 1990s. The K208 set includes remains from at least 400 people. It produced new identifications as recently as 2018.

Jin expected the K55 remains to be highly mixed up — or “commingled,” to use the forensic anthropologists’ term — and they were.

DNA sampling shows K55 contained remains from at least 250 people. About 170 of those are American. The rest are from other countries and believed to be primarily South Korean...