Sexual violence, Sarah Sewall says, “is as old as conflict itself, dating back to a time where our nomadic ancestors spent millennia locked in brutal cycles of raiding and rape.”

What’s different today is that it is often being used “as a weapon of war” by groups that do not feel bound by international humanitarian law and have no official accountability to uphold international human rights, said Sewall, the U.S. undersecretary of State for civilian security, democracy and human rights.

The militant group Islamic State has enslaved about 3,000 women and girls from the Yazidi religious community; female refugees fleeing chaos in Iraq, Syria and other nations have been abused on the road and some have fallen victim to human trafficking and slavery. In Nigeria, Boko Haram extremists have abducted schoolgirls to become slaves and concubines, and women are being gang-raped in Burundi by security forces as they raid the homes of political opponents.