Charles Durning's character portrays a Medal of Honor recipient. In real life, Durning was awarded the Purple Heart three times in WWII for injuries received. In addition to Purple Heart, Durning was awarded the Silver and Bronze Stars for valor and the World War II Victory Medal. In 2008, the French consul presented him with the National Order of the Legion of Honor.
Charles Durning was nominated for a Primetime Emmy Award for Outstanding Guest Actor in a Drama Series for his role as Ernie Yost, a retiree who was a WWII Marine Corporal and medal of honor recipient surrendering himself to NCIS for a murder he claims to have committed in WWII.
Charles Durning, who plays WWII Vet Ernie Yost, was an actual WWII veteran, specifically an Army private first class who was part of the Normandy invasion, survived the Malmedy massacre, and fought in the Battle of the Bulge.
In the scene when Ernie Yost is about to be arrested by the two marines and they are shown the Medal of Honor he's wearing, they snap to attention and salute. While it is tradition to salute a Medal of Honor recipient, contrary to popular belief there is no law or military regulation that requires this other than rendering a salute when it would ordinarily be required.
This is the second time Charles Durning and Mark Harmon worked together. Although not appearing on-screen at the same time, they both previously appeared in The Last Supper (1995) alongside Courtney B. Vance and Cameron Diaz.