Somalia's parliament revolted after Mr Yusuf tried to sack his prime minister
Somalia's President Abdullahi Yusuf Ahmed, an ex-warlord, appears to have fought his last political battle on the national stage after standing down.
He resigned after a fierce power struggle with Prime Minister Nur Hassan Hussein, who was backed by parliament after Mr Yusuf tried to sack him.
The writing was on the wall for Mr Yusuf in December 2008 when the parliament in Baidoa moved to impeach him, accusing him of being a dictator and obstacle to peace.
President Yusuf and his prime minister had been at loggerheads over how to deal with the Islamist-led armed opposition that controls most of southern Somalia.
The embattled president was chosen by the parliament set up in 2004 after years of peace talks in neighbouring Kenya.
But he was unable to achieve his goal of bringing peace to a country that has been engulfed by anarchy since 1991.
Mr Yusuf has long been an ally of neighbouring Ethiopia - one of Somalia's traditional enemies - and a foe of Somalia's Islamists.
In December 2006, he asked Ethiopia to help him oust an Islamist group that had taken power in the capital, Mogadishu, and in much of southern Somalia.
But this foreign intervention was deeply unpopular at home and he was unable to wipe out the Islamists.
The transitional government now only controls parts of the capital, Mogadishu, and the town of Baidoa and Ethiopian forces are due to pull out by the end of December 2008.
Mr Yusuf has survived several assassination attempts.
In Somalia's clan-based politics, he has always suffered the disadvantage of not having a power base in the capital.
He is from the Darod group, based in the northern Puntland region, while the Hawiyes dominate the capital.
He had always named a Hawiye prime minister but this was not enough for some elders from this clan.
Some gunmen from Hawiye militias have joined the ranks of the insurgents.
Born in December 1934, Mr Yusuf is a military strongman and former president of the semi-autonomous region of Puntland.
An army commander in the 1960s who studied in Italy and the former Soviet Union, Mr Yusuf was jailed for refusing to take part in the military coup led by fellow officer Siad Barre in 1969.
In prison, he spent time with the late Somali warlord, Mohamed Farah Aideed.
Mr Yusuf was released in 1975 and three years later, he headed the first attempt to overthrow the Somali dictator.
Somalia has been in anarchy since 1991 when Siad Barre was ousted
It failed and Mr Yusuf was forced to flee to neighbouring Kenya.
From there he led a guerrilla movement aimed at unseating Siad Barre, winning support from Ethiopia - which at that time was at war with Somalia.
But he fell out with the Ethiopians over their claim to areas of Somalia and was jailed in Addis Ababa in 1985.
Mr Yusuf was only released when Ethiopia's Soviet-backed regime fell in 1991.
In the 1990s he returned to his native Puntland, and soon emerged as the region's pre-eminent leader.
Mr Yusuf sought to escape the anarchy that has characterised Somalia since the fall of Siad Barre in 1991, and declared the region autonomous in 1998.
He was a member of an Ethiopian-backed coalition of warlords that blocked previous attempts at restoring order.
As a result of this opposition, the authority of the Transitional National Government (TNG) formed in 2000 was undermined.
In 2001 he was deposed in Puntland, but recaptured the territory a year later - some say thanks to backing from Ethiopia.
Hardline Islamist insurgents have rejected talks with the government
While in power in Puntland, he chased away the al-Itihaad al-Islamiya Islamist militant group, which included Sheikh Hassan Dahir Aweys.
Mr Aweys, accused of having terrorist links by the US, was one of those ousted from Mogadishu in December 2006 and remains one of Mr Yusuf's bitterest opponents.
Mr Yusuf's approach to leadership has been described as authoritarian - and many of his opponents in Puntland have been sacked, jailed or even killed.
One of his friends said: "You're either with the colonel or you are an enemy."
He is a non-smoker and non-drinker and is married with four children.
In the 1990s, he needed a liver transplant and is still not viewed as being in robust health.
Once seen as the strongman Somalia needed, correspondents say Mr Yusuf ended up being perceived as part of the problem and his exit was received with apparent relief by the United Nations, the main broker in ongoing peace talks.