FACTBOX: Chad's Deby, "cowboy of the sands"

(Reuters) - Chadian rebels who have vowed to overthrow President Idriss Deby battled their way into the capital N'Djamena on Saturday and were heading for the presidential palace.

Here are some key facts about Deby:

* Deby was born into the northern Zaghawa tribe in 1952 in Fada, near the border with Sudan in northeastern Chad. He trained at a French military college and learned to pilot helicopters at a base in northern France.

* After returning from military training France in 1979, Deby became President Hissene Habre's chief of staff and was credited with major victories over rebel forces in the 1980s. He won a reputation as a brave and clever tactician. French military sources dubbed him a "cowboy of the sands".

* Deby seized power in 1990, leading a rebel army swathed in desert headgear in a lightning three-week offensive launched from neighboring Sudan's Darfur region to topple Habre, a man accused of instigating tens of thousands of political murders.

* After three months of provisional government, a charter was approved with Deby as president in February 1991. He was re-elected in 1996 and 2001, but international observers noted irregularities in the elections.

* Deby was re-elected a third time in a 2006 ballot boycotted as unfair by opponents. The vote followed a change to the constitution in 2005 that removed a two-term limit for heads of state and an age limit of 70 for presidential candidates. Two thirds of those who voted supported the change.

* At the end of 2005, eight groups opposed to Deby said they had formed a military alliance -- the United Front for Democratic Change (FUC) -- to try to overthrow him.

* The FUC launched an assault on N'Djamena in April 2006, three weeks before Deby's last re-election, but were beaten back by government troops. Deby accuses Sudan of backing the insurgents.

(Writing by London Editorial Reference Unit and Nick Tattersall; Editing by Michael Winfrey)