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Boko Haram Formed
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. -
First Attack
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. -
First Big Loss of Members
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. -
Prison Attack
In the state of Bauchi, 50 Boko Haram militants attack a prison, killing five people and releasing more than 700 inmates. -
Church Targets
Boko Haram targets churches in various states on three Sundays in a row, leaving more than 50 people dead. -
Fake Checkpoint
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. -
Kidnapping
Boko Haram militants kidnap approximately 276 teenage girls from a boarding school in Chibok in Borno. Officials there say some of the girls were able to escape. The kidnapping sparks global outrage and a #BringBackOurGirls campaign on social media. -
Raid
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. -
Pledging to ISIS
In an audio message purportedly from Shekau, Boko Haram pledges allegiance to ISIS, the Islamic militant group which controls areas of Iraq and Syria. -
New Leader
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 al-Barnawi, the son of the group's founder - who was killed by Nigerian security forces in 2009 - is in fact the new leader. -
Mistake Bombing
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.