Short answers, pulled from the story.
The Hazen Brigade Monument at Stones River National Battlefield in Murfreesboro, Tennessee, is the oldest American Civil War monument remaining in its original battlefield location. It was built in 1863 by soldiers of Colonel William Babcock Hazen's brigade while the Civil War was still ongoing.
At the Battle of Stones River on the 31st of December 1862, Hazen's brigade suffered 409 casualties, representing 29 percent of the entire brigade. Forty-five of those men were killed. The brigade defended a four-acre cedar grove called the Round Forest against four Confederate attacks.
Members of Hazen's Brigade built the monument during the summer of 1863, under the direction of Lieutenant Edward Crebbin. The stone inscriptions were carved by two experienced stone cutters from the regiment in 1864. They included the names of officers killed at Stones River and the Battle of Shiloh.
The south face of the Hazen Brigade Monument bears the inscription: HAZEN'S BRIGADE / TO THE MEMORY OF ITS SOLDIERS WHO FELL AT STONES RIVER, DEC. 31ST 1862 / THEIR FACES TOWARDS HEAVEN, THEIR FEET TO THE FOE. The inscription was carved by stone cutters from the regiment in 1864.
Ambrose Bierce served as a staff officer in the 9th Indiana Volunteers, knew Colonel Hazen personally, and fought at Stones River. He visited the monument in 1907 and published "A Resumed Identity" in 1908. That psychological short story uses the Hazen Monument as the pivot of its twist ending.
Workers repairing the monument in 1985 found nine objects deliberately placed about five feet above ground level. These included two 12-pound cannonballs, one 6-pound cannonball, three rifled artillery shells, two rifled musket barrels, and a cedar staff. The National Park Service described these as a "presumptive time capsule," though their intended meaning was never determined.