MAIDUGURI, Nigeria (AP) - Schoolgirls torn from their families in a mass kidnapping and forced into sexual slavery. Bombs that ripped through bus stations. The slaughter of hundreds of villagers, many with their throats cut.
Nigeria has suffered through years of violence from the Muslim extremist group known as Boko Haram, and now its neighbors are starting to take on the militants, too.
African nations are opening up a new international front in the war on terror, discussing Friday the formation of a five-nation force of 7,500 troops to confront the looming regional threat from Boko Haram. The United States promised more technical support, training and equipment.
On Thursday, neighboring Chad sent a warplane and troops that drove the extremists out of a northeastern Nigeria border town in the first such act by foreign troops on Nigerian soil.
"We saw the fighter jet when it started shelling and bombarding the insurgents," said Abari Modu, who watched the attack from a nearby village in Chad, where he had sought refuge. He praised the prowess of the Chadian forces.
Chad's victory, and the need for foreign troops, is an embarrassment to Nigeria's once-mighty military, brought low by corruption and politics. The foreign intervention comes just two weeks before hotly contested national elections in which President Goodluck Jonathan is seeking another term.
The offensive by Chad came days after Boko Haram leader Abubakar Shekau warned Nigeria's neighbors not to intervene.
"African kings ... I challenge you to attack me now. I am ready," he taunted in an Arabic video message translated by SITE intelligence monitoring service. Shekau regularly praises the Islamic State group and al-Qaida.
Boko Haram has declared an Islamic caliphate that now encompasses about 130 towns and villages in a large swath of northeastern Nigeria, according to Amnesty International. The country's 170 million people are split almost equally between a mainly Muslim north and predominantly Christian south.
Global concern has grown in recent months as the terrorist group known for recruiting across borders launched a series of brazen attacks in northern Cameroon even as it increased the tempo and ferocity of attacks on Nigerian soil.
One video this week showed boys learning to shoot assault rifles, with one child appearing to be no taller than his weapon.
In what Amnesty International called the most deadly massacre of the 5-year-old Islamic uprising, Boko Haram killed hundreds of civilians - some say as many as 2,000 - in a Jan. 3 attack on Baga, a border town with a key military base on the northeastern border with Cameroon. Nigeria's military said only 150 people were killed.
Boko Haram attracted international outrage in April when it kidnapped 276 schoolgirls at a boarding school in the remote town of Chibok. Dozens escaped on their own, but 219 remain missing. The U.S., Britain, France and China offered help to find the girls, and Jonathan has repeatedly pledged to return them to their parents, but not one has been rescued. He refused to swap the girls for illegally detained Boko Haram suspects.
Suicide bombings in recent months by young girls - one looked no more than 10 - has raised fears that Boko Haram is using the kidnap victims in its conflict, which has displaced more than 1 million people and killed about 10,000 in the last year, according to the Council on Foreign Relations.
The new multinational force proposed Friday would also be mandated with searching for and freeing all abductees, including the Chibok girls, according to a statement from the African Union.
"We will never forget the girls kidnapped from Chibok last April, and I will never stop calling for their immediate and unconditional release," said U.N. Secretary-General Ban Ki-moon, a guest at the African summit.
"The Boko Haram insurgency poses a clear danger to national, regional and international security," he said.