James Gandolfini playing Col. Winter in The Last Castle

James Gandolfini, star of such films as The Last Castle, Crimson Tide and most recently Zero Dark Thirty, died Wednesday in Italy, from an apparent cardiac arrest. He was 51.

Gandolfini was best known for his portrayals of military figures, although many celebrate his greatest achievement as his HBO documentaries, Alive Day: Home from Iraq, and Wartorn: 1861-2010.

In Alive Day, Gandolfini interviewed ten Iraq War veterans about their experiences in combat and the healing process they went through, both physically and psychologically.

Wartorn examined the phenomenon of Post Traumatic Stress Disorder and its effects on American service members from the Civil War through to 2010, when the film was produced.

Gandolfini's first acting role was as high-strung supply officer Lt. Bobby Dougherty in Crimson Tide. In the film, his character was at odds with Cmdr. Hunter, played by Denzel Washington, and his plan to mutiny in order to deter a nuclear exchange with Russia.

In The Last Castle, Gandolfini portrayed Col. Winter, the commandant of a maximum security military prison. The film raised questions of loyalty, duty and honor in its exploration of the concept of military justice and the difference between what was "legal" and what was "right."

The run-up to the 2003 invasion of Iraq is addressed in the film In the Loop. Gandolfini played Lt. Gen. Miller, an advisor to the U.S. Secretary of Defense. The satirical look at events leading to the outbreak of hostilities in the Middle East received an Oscar nomination for Best Adapted Screenplay in 2010.

His final role, of the CIA Director in Zero Dark Thirty, may have been overshadowed by the harrowing depiction of the hunt for Osama bin Laden, but it stands as his final tribute to the men and women who defend the United States.

The son of a WWII veteran, Gandolfini also took part in USO tours to visit and entertain U.S. troops deployed to Southwest Asia.