[citation needed] In World War II, he enlisted in the United States Marine Corps Reserve in 1942 while finishing his degree, which he completed in 1944.

[6] In the Marines, he trained at Parris Island and Quantico, Virginia, and Officers Candidate School, and was commissioned a second lieutenant.

[citation needed] Other major films included Angels in the Outfield, The Asphalt Jungle, The Next Voice You Hear, Above and Beyond, Kiss Me, Kate, Them!, Oklahoma!, Black Like Me, Guns of the Magnificent Seven, Tora!

He was cast as Father Emil Kapaun in the 1955 episode "The Good Thief" in the ABC religion anthology series Crossroads.

In 1963, Whitmore played Captain William Benteen in The Twilight Zone episode "On Thursday We Leave for Home".

That same year, Whitmore also appeared on an episode of ABC's Custer starring Wayne Maunder in the title role.

In 1969, he played the leading character of Professor Woodruff in the TV series My Friend Tony, produced by NBC.

From 1972 to 1973, Whitmore played Dr. Vincent Campanelli in the short-lived ABC medical sitcom Temperatures Rising.

Whitmore appeared as General Oliver O. Howard in the 1975 television film I Will Fight No More Forever, based on the 1877 conflict between the United States Army and the Nez Percé tribe, led by Chief Joseph.

In 1994, Whitmore appeared in the role of prison librarian Brooks Hatlen in the critically acclaimed and Academy Award-nominated Frank Darabont film The Shawshank Redemption, starring Tim Robbins and Morgan Freeman; Whitmore received much praise for his poignant portrayal of Brooks, the old con and his performance won him a legion of new fans.

In 1999, he played Raymond Oz in two episodes of The Practice, earning an Emmy Award for Outstanding Guest Actor in a Drama Series.

In 2002, Whitmore played the role of the grandfather in the Disney Channel original film A Ring of Endless Light.

In 2003, Whitmore appeared as Josh Brolin's father on the short-lived NBC drama series Mister Sterling, for which he was nominated for an Emmy Award.

"Whitmore, who was an early student at the Actors Studio in New York in the late '40s, taught an acting workshop after moving to Hollywood.

'"[2] Whitmore often returned to New Hampshire to the Peterborough Players, where he got his start in summer stock – in 2008 he played the stage manager in Our Town.

[17] The youngest son, Daniel, was a Forest Service Snow Ranger and firefighter before he launched his own construction company.

These included Elba (a play by Vaughn McBride about an elderly couple who escape from their nursing home); William Gibson's Handy Dandy (he as a conservative judge, she as a liberal nun); and Tom Cole's About Time (in which they played characters identified simply as the Old Man and the Old Woman).

[17] In January 2008, Whitmore appeared in television commercials for the First Freedom First campaign, which advocates preserving "the separation of church and state" and protecting religious liberty.