Boko Haram has been one of the world's deadliest militant groups over the past decade, kidnapping and killing tens of thousands of civilians across northeast Nigeria and beyond.
The Islamic State-linked sect, whose name roughly translates to "Western education is a sin," achieved worldwide infamyafter it kidnapped 274 female high school students from the town of Chibok in April 2014.
This sparked the #BringBackOurGirls campaign — backed by Michelle Obama, Ellen Degeneres, Dwayne Johnson and countless other celebrities.
Some of those girls were released years later, but thousands of other abductees who didn't make the headlines remain missing.
Many of those who weren't enslaved as "wives" and raped are believed to have been used as human bombs — strapped with explosives and sent into crowded markets to cause carnage.
Boko Haram has been involved in some 30,000 killings over the past decade, according to figures from the Council on Foreign Relations, a Washington-based think tank.
How did Boko Haram start?
Boko Haram was founded in 2002 by a charismatic, radical cleric named Mohammed Yusuf. He gained support by speaking out against the rampant corruption and inequality in oil-rich Nigeria.
While he advocated an extreme Islamist ideology, Boko Haram didn't start using violence as a regular tactic until 2009.
The turning point came during July that year when clashes between the group and security forces saw 800 people killed, including dozens of police.
In an attempt to quell the uprising, Nigerian law enforcement and military personnel carried out extrajudicial killings of several prominent Boko Haram figures including Yusuf, according to Human Rights Watch and others.
This allowed a new leader named Abubakar Shekau to take control, and under his rule Boko Haram adopted a strategy of extreme violence.
It has killed Muslims and non-Muslims with impunity, used children as human bombs, burned villages, and kidnapped thousands of men, women and children.
Boko Haram was rated the world's deadliest terror group in 2015 — killing more people than the so-called Islamic State during that year.
What has the U.S. done?
The U.S. dispatched drones and aircraft to look for kidnap victims, and has sent personnel to train Nigerian troops. However, President Barack Obama refused to sell aircraft to the country because of human rights concerns.
International watchdogs say the Nigerian military has been guilty of war crimes during its messy struggle against Boko Haram.
One report by Amnesty International in 2015 detailed gruesome ceremonial killings that involved forcing detainees to dig their own graves and slitting their throats without trial.
In January 2017, the Nigerian Air Force killed more than 100 civilians after it mistakenly bombed a refugee camp while trying to target the group.
President Donald Trump later agreed to sell 12 Super Tucano A-29 planes and weapons to Nigeria in a deal worth $593 million.
What about the Nigerian government?
The government in Abuja has claimed to have killed Shekau on three separate occasions only for the group's leader to resurface alive and well in later videos.
While Boko Haram attacks continue, the level of violence has decreased under Muhammadu Buhari, a former dictator who was elected Nigeria's president in 2015.
However, the group still killed around 1,000 people in the 12 months between May 2017 and May 2018, according to the Council on Foreign Relations.
Boko Haram has also splintered into several factions. One of these, known as Islamic State in West Africa, or ISWAP, has allied itself with ISIS in the Middle East.
Unlike Shekau's faction, ISWAP is believed to distinguish itself by refusing to kill Muslims.
A Reuters report in Apriil 2018 said ISWAP was administering an area of land 100 miles long, creating a taxation economy designed to win over local residents.