One month ago, 110 schoolgirls were kidnapped by suspected Boko Haram militants in the Nigerian town of Dapchi, raising echoes of the infamous abduction of schoolgirls from Chibok in 2014.

President Muhammadu Buhari called the Feb 19. attack a “national disaster” and said the government would not rest until the last girl had been found and released.

The kidnapping was the biggest mass abduction since the Islamist militants snatched about 220 girls from their secondary school in the town of Chibok, sparking an international outcry and starting the viral online campaign #BringBackOurGirls.

Here are 10 key facts about Boko Haram and the Dapchi abductions:

Since 2009, Boko Haram has waged an insurgency to carve out an Islamic state in Nigeria, Niger, Cameroon and Chad that has killed at least 20,000 people and displaced more than 2 million.

Boko Haram in the Hausa language means “Western Education is Forbidden”. More than 2,295 teachers have been killed and 1,400 schools destroyed in northeast Nigeria during its insurgency, according to the U.N. children’s agency UNICEF.

Dapchi, in Yobe state, is roughly 275 kilometers (170 miles) northwest of Chibok. Both are in the northeastern region of Nigeria that has been the epicenter of Boko Haram’s attacks.

Witnesses said that militants arrived in Dapchi on the evening of Feb. 19 in trucks, some painted in military camouflage, and went straight to the school, shooting sporadically and sending students fleeing.

Rights group Amnesty International alleged that security forces had been warned that Boko Haram was on its way to Dapchi but did nothing to stop the attack. Nigeria’s army and police disagreed over who had been in charge of security at the time.

Confusion reigned after the attack, with officials saying two days later that 76 girls had been rescued, only to backtrack on their statement, prompting anger among locals.

The incident is seen as blighting the record of Buhari, who took office three years ago – after the Chibok abduction – with promises to keep civilians safe from Boko Haram.

Last year, Nigeria’s government agreed to pay millions of euros to secure the release of some of the Chibok girls. Boko Haram might have kidnapped the girls from Dapchi in hopes of receiving a similar ransom, a source told Reuters.

Nigeria’s presidency said on March 12 that the government planned to negotiate for the release of the kidnapped girls rather than use a military operation to free them, to ensure that they make it home unharmed.

Boko Haram has increased the use of children as suicide bombers, sending 83 boys and girls to carry out suicide attacks in Nigeria between January and August 2017, compared to 19 children in all of 2016, said the U.N. children’s agency UNICEF. Courtesy: Thomson Reuters Foundation