ON THE EVENING OF Sept. 18, 2007, six men broke into the home of Justine Masika Bihamba in Goma in the Democratic Republic of the Congo. Bihamba wasn’t home, but six of her children, ages 5 to 24, were. The men, reportedly government soldiers, tied up the children at gunpoint and abused two daughters in their 20s, sexually assaulting one with a knife. Bihamba and her children identified the attackers to military police but authorities refused to arrest the suspects, saying there was no evidence against them. They remain free today.

The men targeted Bihamba’s children because of her work coordinating medical and psychological care for women and girls who have been sexually assaulted. In the violent conflict that has raged in Congo for a decade, rape is a weapon of...