(CNN)Here's a look at Boko Haram, a militant Islamic group working out of Nigeria, whose purpose is to institute Sharia, or Islamic law.
Facts
In the local Hausa dialect, Boko Haram means "Western education is forbidden."
The group also refers to itself as Jama'atu Ahlis Sunna Lidda'awati Wal-Jihad, meaning "People Committed to the Propagation of the Prophet's Teachings and Jihad."
Boko Haram militants mainly inhabit areas in the northern states of Nigeria, specifically Yobe, Kano, Bauchi, Borno and Kaduna.
Originally, Boko Haram was referred to locally as the Nigerian Taliban because of their religious similarities to the Taliban.
Boko Haram does not engage in Nigeria's political system out of an adherence to a fundamentalist form of Islam, which forbids participation unless the system is based on Sharia, or Islamic law.
Timeline
2002 - The group, which may have existed since the late 1990s, organizes under the Muslim cleric Mohammed Yusuf. It is centered in Maiduguri, the capital of the northeastern state of Borno.
December 2003 - The first known attack by Boko Haram includes roughly 200 militants, who attack multiple police stations in the state of Yobe, near the Niger border.
July 2009 - The Boko Haram uprising begins in Bauchi and spreads to the states of Borno, Kano and Yobe. The militant group kills scores of police officers. A joint military task force responds, leaving more than 700 Boko Haram members dead and its operational mosque destroyed. The uprising ends when police capture Yusuf. His deputy, Abubakar Shekau, reportedly dies in the uprising. Yusuf later dies in police custody. Police say he is shot during an attempted escape, but Boko Haram claims it is an extrajudicial execution.
July 2010 - Boko Haram releases a video statement in which Yusuf's deputy who allegedly died the previous year, Shekau, claims to be the leader of the group.
September 7, 2010 - In the state of Bauchi, 50 Boko Haram militants attack a prison, killing five people and releasing more than 700 inmates.
May 29, 2011 - The day of Nigerian President Goodluck Jonathan's inauguration, Boko Haram detonates three IEDs near a military barracks in the city of Bauchi. At least 10 people die in the attack.
August 26, 2011 - Boko Haram attacks the United Nations compound in Abuja. A car bomb kills 23 people and injures more than 75 others.
November 4, 2011 - More than 100 people die in multiple attacks in Yobo, Damaturu and Borno states. Boko Haram militants utilize IEDs and vehicle-borne IEDs to target security forces and their offices, markets and 11 churches.
January 2012 - A newly formed splinter group, known as Ansaru, announces Abu Usmatul al-Ansari as its leader.
January 20, 2012 - More than 200 people are killed when Boko Haram launches coordinated attacks targeting police, military, a prison and other targets in the city of Kano in Kano State.
February 19, 2013 - Militants alleging to be Boko Haram kidnap a French family of seven in a national park in northern Cameroon; however, the affiliation with Boko Haram cannot be verified. The family is later released.
April 2013 - Jonathan states he has appointed a team to explore the possibility of amnesty for Islamist militants. Shekau responds in an audio statement: "Surprisingly the Nigerian government is talking about granting us amnesty. What wrong have we done? On the contrary, it is we that should grant you pardon."
April 19, 2013 - Boko Haram battles with multinational security forces from Niger, Nigeria and Chad in the city of Baga in Borno State, leaving nearly 200 people dead, including many civilians. Shekau releases a video in May saying Boko Haram is not responsible for the civilian deaths.
June 4, 2013 - Jonathan approves the proscription of Boko Haram and splinter group Ansaru as terrorist organizations.
June 2013 - Boko Haram targets churches in various states on three Sundays in a row, leaving more than 50 people dead.
August 14, 2013 - The Ministry of Defence announces the death of Boko Haram's second-in-command, Momodu Baba (known as Abu Saad).
August 19, 2013 - Nigeria's chief army spokesperson claims Shekau may have died after an attack on June 30, but the claim is never verified.
September 17, 2013 - Boko Haram gunmen dress in military uniforms and stage a fake checkpoint near Benisheik in Borno, burning vehicles and executing travelers, leaving at least 143 people dead.
September 25, 2013 - A man claiming to be Shekau appears in a video and says that he is alive and well. However, his identity is not verified.
November 13, 2013 - The US State Department adds Boko Haram and Ansaru to its list of terrorist organizations.
April 14, 2014 - Boko Haram militants kidnap approximately 276 teenage girls from a boarding school in Chibok in Borno. Officials say some of the girls were able to escape. The kidnapping sparks global outrage and a #BringBackOurGirls campaign on social media.
May 5, 2014 - In a video statement, a man claiming to be Shekau says, "I abducted your girls. I will sell them in the market, by Allah...there is a market for selling humans. Allah says I should sell. He commands me to sell. I will sell women. I sell women."
May 13, 2014 - Hundreds of Boko Haram militants storm three villages in the state of Borno. Villagers resist, killing more than 200 Boko Haram fighters.
May 20, 2014 - Twin blasts in the city of Jos kill 118 people at a market. Nigerian authorities describe the blasts as "terrorist activities" but decline to speculate on who might be responsible.
May 21, 2014 - The White House announces that the United States has sent 80 troops to Chad to help search for the kidnapped schoolgirls.
May 22, 2014 - The UN Security Council adds Boko Haram to its sanctions list.
June 3-4, 2014 - Hundreds of people are killed in raids by Boko Haram militants in the state of Borno, with some sources putting the death toll at 400 to 500.
June 7-8, 2014 - Suspected Boko Haram militants kidnap at least 20 young women over a weekend in the northeastern Nigeria village of Garkin Fulani, eight kilometers from a town where more than 200 schoolgirls were taken nearly two months earlier.
June 18-22, 2014 - Boko Haram militants hold the village of Kummabza in Borno state hostage for four days. They abduct more than 60 females, including children, and kill 30 men in the raid.
July 7, 2014 - Sources say at least 57 girls kidnapped by Boko Haram last month from the Kummabza village have escaped from their captors and returned to their village. Boko Haram is still believed to be holding about 200 schoolgirls abducted April 14 from a boarding school in the town of Chibok.
July 17-20, 2014 - Boko Haram raids the Nigerian town of Damboa. By the time the raid ends, 66 residents have been killed and more than 15,000 have fled.
October 16, 2014 - The Nigerian government announces it has reached a ceasefire agreement with the Islamist terror group that includes the promised release of more than 200 kidnapped schoolgirls.
November 1, 2014 - In a video, the group's leader denies the Nigerian government's claim of a ceasefire.
January 3, 2015 - A multi-day raid begins, where hundreds of Boko Haram gunmen seize the town of Baga and neighboring villages in northern Nigeria, as well as a multinational military base, leaving bodies scattered everywhere and as many as 2,000 people feared dead.
March 2, 2015 - Boko Haram releases a video showing the apparent beheadings of two men they suspected of being spies.
March 7, 2015 - In an audio message purportedly from Shekau, Boko Haram pledges allegiance to ISIS, the Islamic militant group which controls areas of Iraq and Syria. The affiliate is named "Wilayat Gharb Afriqiyya," which means the Islamic State of West Africa.
March 12, 2015 - In an audio message purportedly from an ISIS spokesman, the group announces that the caliphate has expanded to western Africa and that ISIS leader Abu Bakr al-Baghdadi has accepted Boko Haram's pledge of allegiance. On the same day, ISIS blows up the Iraqi army headquarters north of Ramadi, killing at least 40 Iraqi soldiers.
April 25-26, 2015 - The decomposed corpses of at least 400 men, women and children are found in shallow, mass graves and on the streets of Damasak in northeastern Nigeria. Due to a joint Nigerian-Chadian military operation, the town has recently been freed of Boko Haram, which seized the town in November.
April 28-April 30, 2015 - Nigerian troops rescue about 450 women and girls in the Sambisa Forest during a military operation centered around destroying Boko Haram camps and rescuing civilians. According to the military, none of those rescued have been identified as the Chibok schoolgirls kidnapped last April.
July 1, 2015 - Boko Haram militants raid three villages in the northeastern Nigerian state of Borno, killing at least 145 people, according to witnesses.
September 3, 2015 - An estimated 30 people are dead and 145 injured after Boko Haram militants attack a crowded market in Kerawa, Cameroon, and an infirmary near a Cameroonian military camp, according to Cameroonian military spokesman Col. Didier Badjeck.
September 23, 2015 - Two hundred forty-one women and children are rescued and 43 Boko Haram militants are arrested after the Nigerian military raids camps run by the terrorist group in two villages.
February 2016 - Militants from Boko Haram attack two villages in northeast Nigeria, killing at least 30 people. In another attack, two female suicide bombers kill 58 people at a Nigerian refugee camp for villagers fleeing terrorism. A suspect in the attack on the camp tells officers that she and the two suicide bombers were dispatched by Boko Haram.
April 14, 2016 - CNN posts a video of some of the teenage girls abducted from Chibok that was sent to negotiators by their captors as a "proof of life."
May 17, 2016 - Amina Ali Nkeki, one of more than 200 kidnapped Chibok schoolgirls, is the first to be freed after two years in captivity. Nigeria's army says she was rescued by army troops, but a witness tells CNN the girl wandered out of the Sambisa Forest in the northeast of the country along with her child and a man.
August 3, 2016 - ISIS publication al-Naba says that Sheikh Abu Musab al-Barnawi is the new leader of Boko Haram. A Boko Haram insider confirms to CNN that Barnawi, the son of the group's founder -- who was killed by Nigerian security forces in 2009 -- is in fact the new leader.
August 14, 2016 - Boko Haram releases a video of some of the girls kidnapped in April 2014 and demands the release of Boko Haram fighters in exchange for the girls.
October 13, 2016 - Boko Haram militants hand over 21 Chibok schoolgirls to authorities after a series of negotiations with the Nigerian government. It's the first mass release of any of the more than 200 girls and women kidnapped from their school in April 2014.
January 5, 2017 - The Nigerian army says another missing Chibok girl and her 6-month old baby have been located during an operation to arrest suspected Boko Haram terrorists.
January 17, 2017 - Scores of people are killed when a Nigerian fighter jet mistakenly bombs a camp for the internally displaced during an operation in Rann against Boko Haram militants, according to Nigerian officials and the Red Cross. The Nigerian government provides no official death toll, but humanitarian aid group Doctors Without Borders says "about 90" people died.
May 6, 2017 - Eighty-two Chibok schoolgirls are released after negotiations between Boko Haram and the Nigerian government.
February 19, 2018 - A faction of Boko Haram raids the Government Girls Science and Technical College in the northeast Nigerian town of Dapchi, kidnapping 110 students of the college.
February 19, 2018 - A Justice Ministry statement says that a Nigerian high court has convicted 205 Boko Haram suspects for their involvement with the insurgent group, and the suspects were sentenced to jail terms ranging from three to 60 years. The court also freed 526 suspects, including minors, for lack of evidence and ordered they be sent to their state governments for "proper rehabilitation."
March 1, 2018 - Boko Haram militants attack a displacement camp in Rann, Borno State, killing at least three Nigerian aid workers and injuring three others. Three International Committee of the Red Cross (ICRC) aid workers are abducted in the attack. On September 17, the ICRC says abducted aid worker Saifura Hussaini Ahmed Khorsa, 25, has been killed. Abducted midwife Hauwa Mohammed Liman is executed after a deadline for negotiations expires, the Nigerian government says on October 16.
March 21, 2018 - Minister of Information and Culture Alhaji Lai Mohammed says 104 of the girls abducted from their boarding school on February 19 have been released and returned to their hometown of Dapchi. Six of the Dapchi schoolgirls are still missing. Mohammed also later clarifies that two others who were kidnapped, "who are not students of the college -- a primary school boy who came to the school to sell pure water and another primary school girl," were released as well.
April 13, 2018 - UNICEF says Boko Haram has kidnapped more than 1,000 children in northeastern Nigeria since 2013.
May 7, 2018 - The Nigerian army says it has rescued more than 1,000 Boko Haram captives -- mainly women and children, as well as some young men who had been forced to become Boko Haram fighters -- in Borno state. The operation, which was conducted in conjunction with Cameroonian and Nigerian troops of the Multinational Joint Task Force (MNJTF), rescued the hostages from Malamkari, Amchaka, Walasa and Gora villages of the Bama Local Government Area.
May 24, 2018 - Amnesty International releases a report claiming women and girls who have fled Boko Haram are being raped by Nigerian soldiers, starved and forced to exchange food for sex. The Nigerian government tells CNN the military found cases of abuse in these camps during the period mentioned in Amnesty's report in 2015 and meted out appropriate punishment, countering an army spokesman's claims that the allegations were investigated and found not to be true. Both the government and army spokesman accuse Amnesty of "recycling" claims from a previous report.
January 29, 2019 - The UN Refugee agency says escalating attacks by Boko Haram militants have forced 30,000 people out of Nigeria's northeast into Cameroonian borders over the weekend. The United Nations says more than 250,000 people have already been displaced from northeast Nigeria, and surging militant attacks targeting civilians have forced thousands more to run for their lives each day.
April 14, 2019 - On the fifth anniversary of the kidnapping of girls from Chibok, Nigerian President Muhammadu Buhari reiterates his promise that "we will not rest until all the remaining girls are back and reunited with their families."
May 10, 2019 - UNICEF says 894 children, including 106 girls, who were recruited by the anti-Boko Haram militia Civilian Joint Task Force (CJTF) in northeast Nigeria, have been released. UNICEF says 1,727 children have been released since CJTF signed an action plan in 2017 to end child recruitment.
July 27, 2019 - A suspected attack by Boko Haram on a funeral gathering in northeastern Nigeria leaves at least 65 people dead. A local official says 21 people were initially killed during the burial ceremony, and an additional 44 people were killed when villagers ran after the assailants.
February 9, 2020 - At least 30 people, including a pregnant woman and a baby, die after suspected Boko Haram militants set fire on sleeping travelers in Borno state, Nigeria.
June 9, 2020 - At least 81 people are killed in an attack on a village by suspected Boko Haram militants in northeast Nigeria, the Borno state government said in a statement. Seven people, including the village head, children and women, are abducted.
January 28, 2021 - Some of the Chibok schoolgirls escape from their captors, the father of one of the girls tells CNN.
April 26, 2021 - Boko Haram fighters have reportedly hoisted the Islamist group's flag in a remote district in Niger State, Nigeria's Middle Belt region, and seized the wives of fleeing residents, the state's governor says in a widely circulated video. Niger State Governor Abubakar Bello discloses during a visit to an internally displaced persons camp in the state capital Minna, that over 3000 persons have been ousted from their communities by Boko Haram and other criminal gangs locally known as bandits.
June 6, 2021 - The Islamic State West African Province (ISWAP) militant group says in an audio recording heard by Reuters that Boko Haram leader Shekau is dead. Shekau died around May 18 after detonating an explosive device when he was pursued by ISWAP fighters following a battle, a person purporting to be ISWAP leader Abu Musab al-Barnawi says on the audio recording. A Nigerian intelligence report shared by a government official and Boko Haram researchers have also said Shekau is dead.
