Lagos-Boko Haram has claimed more than 20,000 deaths, displaced 2.6 million people from their homes, and kidnapped thousands of children but the kidnapped Chibok girls continue to define the group’s insurgency.

On Sunday, the Chibok girls, who were captured in April 2014, were back in the spotlight after a Boko Haram video purportedly showing some of them was released, following months of silence and speculation about their fates.

Although it is unclear when the video was shot and if the girls are all from Chibok, experts say its release date is not a coincidence.

Boko Haram is going through a leadership crisis after pledging allegiance to ISIS in March 2015, with ISIS appearing earlier this month to have appointed Abu Musab al-Barnawi chief of the group.

Abubakar Shekau, Boko Haram’s leader since 2009, could be using the new video to show his control over the Chibok girls, arguably Boko Haram’s biggest asset, said Kyle Shideler of the Washington-based Center for Security Policy.

“The video serves as a message to the Nigerian government that despite being replaced, Shekau still has bargaining chips and will have to be dealt with,” Shideler told Agence France Presse.

“It is also a reminder that the group’s largest propaganda success, the Chibok girls kidnapping, occurred under Shekau’s leadership.”

-Of the 276 girls kidnapped from the Government Girls Secondary School in the northeastern town of Chibok, 218 are still missing.

Dozens managed to escape in the early hours of the abduction, and one of them was found in May.

The audacity of the mass kidnapping — and the failure of the Nigerian government to find the girls — shocked the world.

Boko Haram catapulted from an obscure regional threat to a high-profile terror group, as politicians and celebrities around the globe posted the #bringbackourgirls hashtag on social media.

The response was “unique”, said Yan St-Pierre, head of the Modern Security Consulting Group in Berlin.

“While other hostages held by terrorists have also caused some media interest — the Israeli soldier Gilad Shalit in Palestine or the Iran hostage crisis in 1980, for example — it was rather localized,” he said.

“But in the case of the Chibok girls, the media reaction was international.”

The interest in the Chibok girls transformed them into a valuable asset for Boko Haram.

“It is both a blessing, because they were protected a little, and a curse, because they have become Boko Haram’s bargaining chip,” St-Pierre said.

On April 14 this year, the two-year anniversary of the kidnapping, UNICEF said that “up to 7000 women and girls might be living in abduction and sex slavery,” often forcibly married or used as suicide bombers.

“These are only estimates, the number is probably much higher,” Toby Fricker of UNICEF Nigeria told AFP.

Human Rights Watch revealed in early August that over the past three years 10,000 young boys had been kidnapped, with some of them being trained as soldiers.

The Chibok girls were not even the largest group of children who were kidnapped.

The largest abduction took place in November 2014, when 300 children were taken from the town of Damasak in Borno State, according to Human Rights Watch.

“The girls of Chibok are a symbol,” said Munir Safieldin, a U.N. humanitarian coordinator.

He said they represent tens of thousands of victims and that in many ways their saga encapsulates the entire conflict.

While the Nigerian army has won many military victories, the northeast of the country is ravaged after years of fighting Boko Haram.

With tens of thousands of children at risk of dying from starvation, it will take more to end the war than just bringing the Chibok girls back home.