It’s thought up to 4,000 Russian men travelled to Syria and Iraq to fight for so-called Islamic State.
Now the caliphate has collapsed, and many of those militants have been killed, Russian officials are facing appeals from hundreds of families to bring back IS wives and children.
Initial moves to return some of the women stalled after the FSB security service declared them a threat. But dozens of children have already been brought home.
Our correspondent, Sarah Rainsford, went to the southern Russian republic of Dagestan to meet some of them.