Rebel groups have played a key role in Chad's long history of instability, dating back to when the vast semi-desert country gained independence from France in 1960.
Over the decades, armed groups have made repeated attempts on power, striking from havens in neighbouring Libya or Sudan.
More than 40 on Monday signed a deal with the ruling junta to join a national forum, starting August 20, which is supposed to pave the way to elections.
But some have refused to endorse the agreement, including two of the biggest groups.
Here's a snapshot:
- Front for Change and Concord in Chad (FACT) -
One of the largest groups in terms of fighters and weaponry, the FACT emerged in 2016 from a split in a rebel force called the Union for Democracy and Development (UFDD).
It ranges over northern Chad, a restive and lawless desert region abandoned to illegal gold miners and gangs of traffickers, but it also runs rear bases across the border in Libya.
It was while leading operations against the FACT in northern Chad in April 2021 April that iron-fisted veteran president Idriss Deby Itno sustained fatal wounds.
His son, General Mahamat Idriss Deby Itno, took over, fronting a 15-member military junta.
In the following weeks, the armed forces killed several hundred rebels and took nearly 250 prisoner and the FACT retreated into Libya, according to the authorities.
The FACT's leader is Mahamat Mahdi Ali, who studied in France, where he was also a Socialist Party activist.
The front has refused to sign Monday's agreement, saying the deal fails to take its demands into account, including the release of more than 300 of its fighters.
-Union of Resistance Forces (UFR) -
Created in 2009 from an alliance of eight groups, the UFR draws its fighters mainly from the Zaghawa ethnic group, from which the elder Deby hailed.
They are led by his nephew, Timan Erdimi, who fled to Qatar for a decade after falling into disgrace. Erdimi's brother is in jail in Egypt.
In February 2019, the UFR mounted an attempt to oust Deby by sending a column of fighters in 50 pickup trucks from Libya via Sudan.
They were beaten back by French air strikes, requested by Deby, a major ally in France's anti-jihadist campaign in the Sahel.
The UFR is estimated to have several hundred men, based in southern Libya and northern Chad.
The group is a signatory of Monday's accord.
- Union of Forces for Democracy and Development (UFDD) -
The UFDD was created in 2006 by Mahamat Nouri, a former close aide to Hissene Habre, the president overthrown by the older Deby in 1990.
Habre was sentenced in 2016 to life imprisonment by a special court under the aegis of the African Union for crimes against humanity.
Nouri joined up with Deby and for a time became his defence minister before defecting.
In early 2008, the UFDD, with other rebels, reached the gates of the presidential palace in N'Djamena. Supporting the regime, France secured the capital's airport, allowing the army to obtain more ammunition. The offensive was repelled.
In 2019, Nouri was indicted in France for "crimes against humanity" for recruiting child soldiers in Chad and Sudan.
Incarcerated in Paris, he was released in 2020 for health reasons.
The Libyan-based UFDD was greatly weakened when it splintered in 2016 and the FACT emerged. In 2019, several hundred UFDD fighters joined the Deby regime.
The UFDD is also a signatory of the deal.
- Military Command Council for the Salvation of the Republic (CCMSR) -
The CCMSR was formed in June 2016 after a rift in the FACT.
In a report issued in December 2019, UN experts on Libya said the CCMSR was "most likely steeped in criminal activities and trafficking of all kinds, linking southern Libya to the Tibesti region in Chad".
Chadian rebel groups are also regularly accused of selling their services as "mercenaries" to the two rival powers battling for control of Libya.
On its Facebook page, the CCMSR says it refused to sign Monday's agreement, declaring that the "principles for which we are fighting do not enable us to join a dialogue whose goals we do not know."
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