The siege of Vicksburg, which began in mid-May 1863, lasted an incredible 47 days. As it progressed, the Reverend Mr. William Lovelace Foster, conscious of the drama and the tragedy taking place around him and of which he was a part, decided to write his wife a letter describing life in the beleaguered city. Foster began his letter on June 20 and wrote "at broken intervals of time," with many interruptions, "in the midst of danger" from bullets and exploding shells. By the time the siege had ended and Vicksburg had surrendered on July 4, 1863, Foster's letter had grown to 79 pages.

Foster described the siege from the vantage point of the ordinary soldier—the enlisted man and junior officer with whom he associated daily, and to whom he ministered as army chaplain. A good reporter and a perceptive observer of human nature, Foster produced a unique eye-witness account of one of the most dramatic events of the Civil War. Describing the horrors of 19th-century warfare in realistic detail, revealing much about the good and the bad traits of men subjected to the torments of a protracted siege, refusing to soften war's grim miseries with any romantic gloss, Foster bore witness to the spirit of the men who endured the siege of Vicksburg.