Rise to power
Deby's loyalty to Habre earned him the position of commander-in-chief of the Chadian army.
After defeating pro-Libyan forces in 1984 in Eastern Chad, Deby was removed from his post, and was later appointed as chief military adviser to the president.
With the increasing power of the presidential guard, a division emerged between Habre and Deby, which forced Deby to flee to Libya, and then later move to Sudan and form the Patriotic Salvation Movement (PSM).
The PSM was supported by Libya and Sudan, and started rebel operations against Habre in 1989.
Successful coup
Deby's troops marched into the capital of Ndjaména and took hold of the Chadian government.
Six years after seizing control of the government, Deby then established and won the country's first multi-party elections in 1996.
In 2001 he was re-elected for a second term, but rebellions against him started in 2005. Rebel groups accusing the president of being corrupt and holding unfair elections.
International observers said that the elections were not free and fair.
New elite
Deby was then forced to disband his presidential guard and form a new elite military force after large-scale desertions from Chad's army took place in 2004 and 2005.
This move weakened his position as president and encouraged the growth of armed opposition groups who said he ruled like a dictator.
Deby ammended the constitution so that in 2006 he could be re-elected as president for a third term.
Opposition parties boycotted the 2006 presidential elections.
Corruption
Accusations of corruption have continued during Deby's presidential tenure.
In mid-2006, the World Bank froze an oil revenue account in dispute over how Chad had spent the money.
The oil revenue was initially set up to be allocated to the country's health, education and infrastructure programs.
He has also been said to favour members of his Zagawa clan, whom he filled his government and armed forces with.