John Vincent Brennan (August 16, 1937 – October 20, 2023) was a United States Marine Corps officer and political aide.

[3] In 1969, then-Major Brennan was appointed a Marine Corps Aide to President Nixon; during that time he rose to Colonel.

[2] When Nixon returned to La Casa Pacifica in San Clemente, California, nicknamed "The Western White House" during his administration, Brennan left the Marines and served as the ex-president's chief of staff.

[2] He originally refused the position after some of Nixon's associates made it sound like a business proposal; the financial aspect was not of interest to Brennan.

However, after repeated requests from Nixon, Brennan agreed to leave his career of over 16 years and join the former president's staff.

Due to the circumstances of Nixon's departure, he did not receive the level of information and courtesy offered to previous former presidents.

[3][4] When Bob Woodward and Carl Bernstein released their 1976 book, The Final Days, Brennan felt that it did not correspond with his own time with the former president, but he stated "as a fictitious novel, it reads well.

Brennan originally turned the idea down, but after discussing the situation with his staff, agreed that Nixon should voluntarily go further and that some expression of regret for Watergate needed to be put on record.

He also noted that a scene in the film where he is portrayed threatening Frost over the phone if he got the facts wrong, never occurred and was made up by Morgan for dramatic purposes; however, he did warn Frost, in person over lunch, not to re-edit the footage to change the focus to make Nixon look bad.