I stood in high Pennsylvania winds last Sunday morning on what is ground zero to the core story of Mission: Jimmy Stewart and the Fight for Europe. At my back was Gettysburg’s infamous Wheatfield, scene of some of the bloodiest fighting of the second day’s battle. A half mile at my front rose Little Round Top. And staring me in the face was a granite monument to the 11^th Pennsylvania Reserves, the regiment commanded by Col. Samuel M. Jackson. In murderous fighting on July 2, 1863, the 11^th Pennsylvania—part of Fisher’s Brigade of the Fifth Corps—was part of a charge down the slope of Little Round Top that checked Longstreet’s ambitious maneuver to hit the federal left flank. Afterward, a Union commanding general rode up to Jackson hat in hand and exclaimed, “Colonel Jackson, you have saved the day. Your regiment is worth its weight in gold; its weight in gold, sir!”

Thanks to men like Col. Sam Jackson, the Union was preserved.

Why is this ground zero to Mission? Sam Jackson was Jimmy Stewart’s grandfather, his mother’s father. Jackson’s regiment had been positioned at the foot of Little Round Top and received orders to hold against the Confederate advance at all cost. This his regiment did, and advanced probably no more than 1,500 yards that day, but hard-fought and bloody real estate it was. Standing amidst the monuments to so many regiments intermingled there and representing both Union and Confederate units, this hallowed acreage, I was hit by what Jackson had done, and how much it influenced James Maitland Stewart, the laid-back star of stage and screen.

Except Stewart wasn’t laid back at all. Stewart was high-strung and possessed a compulsion to serve—his Mission of the book title—that was born of his two grandfathers, Sam Jackson and James Maitland Stewart, Jim’s father’s father and a sergeant in the Army Signal Corps. Sergeant Stewart had fought his way through many Civil War battles, the last being Appomattox, where he then witnessed the surrender of Lee to Grant that ended the war. The estimable Jackson had died just before Jim was born in 1908, but old J.M. lived into the 1930s and Jim learned about service and sacrifice from this man above all others, one who had lived through America’s bloodiest war.

This past Sunday, November 20, I lectured at the Gettysburg Heritage Center, which includes an ambitious multi-media museum designed to entertain and educate even today’s short-attention-span learners. When I described Jackson’s advance and his connection to Jim to a packed Heritage Center house, there was a collective gasp. People just don’t realize what a giant shadow Jim’s grandfathers cast on his life. In effect, Jim was poured into a military mold and had no choice but to end up a soldier. It’s the reason he gleefully reported for induction after being drafted nine months before Pearl Harbor. With this action he turned his back on Hollywood luxury, a thriving avocation as a sexual athlete, and an Academy Award career with a giant, goofy grin and pulled an army private’s uniform onto his six-foot-four, 139-pound frame. After he was fingerprinted and sworn in before a throng of reporters and cameraman, Jim refused to talk to or work with the press for the next five years so he could concentrate on being the best soldier he could be. It’s unprecedented what he did and the way he did it.

Speaking of soldiers, I shared the microphone last Sunday with Clem Leone, 92-year-old veteran of the air war over Europe. Clem knew and flew with Stewart as described in Mission, and was shot down over Gotha, Germany, on February 24, 1944. I’ve never experienced anything quite like this stretch of two hours, sharing the stage and then sitting and signing books with my own hero who had lived history. It’s one of many things I’m thankful for this Thanksgiving 2016.