Hakan Fidan, the head of Turkish intelligence, is seen as one of the key players behind the announcement by Abdullah Ocalan, the jailed Kurdistan Workers' Party (PKK) leader, of a ceasefire in the country's decades-old conflict.
Fidan, 45, was appointed to the top spy seat by close ally Recep Tayyip Erdogan, the Turkish Prime Minister, in May 2010.
He took part in peace talks with senior figures from the PKK in Oslo in 2009, which unravelled in 2011 when secret recordings were leaked to the media revealing the discussions.
After the failed negotiations, Erdogan's government delegated Fidan to hold talks with Ocalan, who is serving a life sentence on the isolated prison island of Imrali, near Istanbul.
When state prosecutors last year asked the senior intelligence official to shed light on whose authority the agency held the Oslo talks, Erdogan publicly voiced support for his ally.
"He is my secret-keeper, he is the state's secret-keeper"
- Recep Tayyip Erdogan
"It was me who sent him to Oslo and to Imrali," the premier said.
"He is my secret-keeper, he is the state's secret-keeper" Erdogan said, describing Fidan as a "very well-trained bureaucrat."
Erdogan's ruling party later introduced a bill in parliament requiring the prime minister's authorisation to interrogate the spy agency's agents, effectively immunising Fidan from any prosecution.
Details about Fidan's life are largely confidential because of his role at the top of Turkey's National Intelligence Organisation (MIT).
According to a brief resume on the MIT's official website, Fidan served in the Turkish Armed Forces as a non-commissioned officer. He also worked at NATO's Germany-based Allied Rapid Reaction Corps.
The married father-of-three has a bachelor's degree in political science and government from the University of Maryland University College.
He also earned a master's and a doctoral degree at Ankara's private Bilkent University.
Fidan headed a public agency for development known as TIKA, which is active in the Turkic states and Africa but also in other Muslim countries where Turkey has been trying to gain a foothold as part of its strategy to become a regional power.
Local media have reported that he fostered ties with an influential Islamic movement headed by Fethullah Gulen, who lives in exile in the US, during his four-year tenure at TIKA.
The Gulen movement, which has dozens of schools abroad, is considered close to Erdogan's Islamic-rooted Justice and Development Party, in power since 2002.
Before he was appointed the new head of MIT, Fidan worked in Erdogan's office as a deputy undersecretary. He is also known to have worked closely with Turkish Foreign Minister Ahmet Davutoglu.
Following Fidan's MIT appointment in 2010, Israeli daily Haaretz reported that the Israeli defence establishment, particularly Mossad, viewed his promotion with concern, accusing him of steering Turkey away from the Israel and closer to Iran.
The paper cited unnamed Israeli sources as speculating that Fidan, along with Erdogan and Davutoglu, orchestrated a change in Turkish-Israeli ties - which were wrecked after Israeli commandos raided a Gaza-bound aid flotilla, killing nine Turks on board.
In an opinion piece last year, Fatih Altayli, the editor in chief of the daily Haber-Turk, claimed that Erdogan was grooming Fidan for the post of prime minister.
"He [Erdogan] brings Fidan along in many important talks with foreign heads of state. It feels like he is considering Hakan Fidan for an important mission in the future," Altayli said.
If Fidan's efforts continue to bear fruit, the peace talks could lead to the disarmament of about 4,000 PKK fighters in southeast Turkey and northern Iraq and, ultimately, to the end of a 29-year-old rebellion that has cost some 45,000 lives, mostly Kurdish.