Brennan's early career:
Brennan was the son of Irish immigrants. He grew up in North Bergen, New Jersey, and attended St. Joseph of the Palisades High School in West New York, New Jersey, before earning a B.A. in political science from Fordham University in New York City in 1977. As an undergraduate he also studied at the American University in Cairo (1975–76), where he learned Arabic. In 1980 he was awarded an M.A. in government (with a concentration in Middle Eastern studies) from the University of Texas at Austin.
Responding to an employment listing in The New York Times, Brennan began his long career in the CIA in 1980. After joining the Directorate of Intelligence (DI), the agency’s analytic branch, in 1981, he served with the State Department as a political officer at the U.S. embassy in Jiddah, Saudi Arabia (1982–84). He then had a variety of analytic assignments in the DI’s Office of Near Eastern and South Asian Analysis (1984–89) before directing terrorism analysis at the Director of Central Intelligence’s Counterterrorist Center in the early 1990s. After acting as the CIA’s daily intelligence briefer for U.S. Pres. Bill Clinton (1994–95), he served as the agency’s chief of station in Saudi Arabia (1996–99), as chief of staff to CIA Director George Tenet (1999–2001), and as the CIA’s deputy executive director (2001–03). Thereafter he spearheaded the efforts of a number of agencies in forming the organization that became the National Counterterrorism Center, which he led as interim director before retiring from the CIA in 2005.
https://www.britannica.com/biography/John-Brennan