Martin Callinan, who has resigned as Garda Commissioner in a shock move this morning, had been a member of An Garda Siochana for 41 years and had been commissioner for just over three years.
He was due to retire on age grounds when he reached 60 years of age last August but was offered a two-year extension by Government to continue on in the post for a further two years.
He was set to retire in August of next year.
The married father of three is from Glasnevin, north Dublin, and was aged 57 years when appointed by Government to the post of commissioner in December 2010.
He was the first Dubliner in the 82-year history of the force to be appointed Garda Commissioner.
Minister for Justice Dermot Ahern nominated Mr Callinan for promotion saying at the time he had a "distinguished record of service in the Garda Síochána, with a wide range of experience in key positions in the force, and has all the qualities needed to lead the Garda Síochána successfully through the challenging times ahead."
He assumed the post from his predecessor Fachtna Murphy who retired at the time on age grounds after, like Mr Callinan, being offered an extension to continue serving despite reaching retirement age.
Mr Callinan was, at the time of his promotion, one of the two deputy commissioners, the second highest rank in the force. He and fellow deputy commissioner at the time Nacie Rice were regarded as the two clear favourites to succeed Mr Murphy.
In his previous role, Mr Callinan was head of operations across the force, meaning he was in charge of all operational policing in the Republic. In that post he also had overall responsibility for anti-terrorism operations and all national Garda units, including the Garda National Drugs Unit, Criminal Assets Bureau and Organised Crime Unit.
The six regional assistant commissioners and the assistant commissioners in crime and security, national support services and traffic were also under his command when he was a deputy commissioner.
He assumed control of the Garda at a time when the record 14,500 strength of the force was just about to begin falling because of the recruitment ban. It has now dropped to 13,000 just as new recruits are about to start entering the training college in Templemore, Co Tipperary, for the first time in five years.
Crime had begun to fall when he took over at the head of the force and almost all crime categories have continued to show significant falls during his stewardship.
Road deaths had also reached record lows during his term, but have begun to increase slightly of late, with many believing the reduction in Garda numbers and overtime budgets has meant an easing in enforcement of drink driving laws and other measures.
Mr Callinan joined An Garda Síochána in 1973 and in his early years, served in Waterford, Blanchardstown, Cabra, the former Central Detective Unit, Pearse Street, Terenure, Swinford and the crime and security section at Garda Headquarters in Phoenix Park, Dublin.
He was appointed assistant commissioner in 2005, and in January 2007 he became a deputy commissioner.
He holds a BA in police management. In 1995, he undertook management training at the FBI Academy, Quantico, Virginia, where he also recently completed the national executive institute programme which is designed for police chiefs from around the world.