Boko Haram kidnapped 274 school girls in 2014, and in 2016 released a video in which some of the girls are seen pleading for help in the form of a prisoner exchange.  Eighty-two of the school girls have been released in exchange for at least five Boko Haram commanders.

Reuters reports:

Boko Haram militants have released 82 schoolgirls out of a group of more than 200 whom they kidnapped from the northeastern town of Chibok three years ago in exchange for prisoners, the presidency said on Saturday.

. . . .  Nigeria thanked Switzerland and the International Committee of the Red Cross for helping secure the release of the 82 girls after “lengthy negotiations”, the presidency said in a statement.

. . . .  A military source said the girls were brought on Sunday morning from Banki near the Cameroon border to Maiduguri, the capital of Borno state where the insurgency started.