The new Garda Commissioner, Fachtna Murphy, has reshuffled his senior management team after formally taking over from Noel Conroy on Wednesday.
Deputy Commissioner Martin Callinan will succeed Mr Murphy as Deputy Commissioner in charge of operations where he will direct the investigation of organised crime.
Mr Callinan was promoted to Deputy Commissioner in January with responsibility for strategy and change management. Regarded as Mr Murphy's strongest rival to succeed Mr Conroy, he had been assistant commissioner in charge of national support services, including all of the specialist investigative units.
Mr Callinan, from Dublin, has been a garda for 34 years. He has served in detective positions in Dublin, Waterford and Mayo.
Deputy Commissioner Peter Fitzgerald moves from his role in charge of strategic and resource management to fill the post vacated by Mr Callinan. His new posting will focus on change across the force. He has spent most of his service in the Dublin region and has served extensively overseas with international bodies including the UN.
John Leamy, a former assistant secretary at Revenue, assumes the new role of chief administrative officer.
His appointment is one of several civilian positions created on the recommendation of the Garda Inspectorate in a move to bring more non-policing expertise to the force.
Mr Murphy paid tribute to Mr Conroy, saying he had given 44 years of distinguished service.
"His dedication and professionalism were an example to all who worked with him over that time," he said. "He provided strong leadership to the organisation and guided it through some challenging events and decisions.Noel's retirement is well-earned and truly deserved."
Mr Murphy, who was deputy commissioner in charge of operations, has been a garda since 1967.
A native of Timoleague, Co Cork, he was a detective in Dublin who came to prominence when as a detective chief superintendent he took charge of the Criminal Assets Bureau (Cab) on its inception in 1996 after the murder of Veronica Guerin.
Much of the case law on which the bureau operates was established under his stewardship.He has studied policing in the US and UK at degree and postgraduate level.