Despite the thousands of books and articles written about Gettysburg, Tom Ryan's groundbreaking Spies, Scouts, and Secrets in the Gettysburg Campaign: How the Critical Role of Intelligence Impacted the Outcome of Lee's Invasion of the North, June - July 1863 is the first to offer a unique and incisive comparative study of intelligence operations during what many consider the war's decisive campaign.

Based upon years of indefatigable research, the author evaluates how Gen. Robert E. Lee used intelligence resources, including cavalry, civilians, newspapers, and spies to gather information about Union activities during his invasion of the North in June and July 1863, and how this intelligence influenced General Lee's decisions. Simultaneously, Ryan explores the effectiveness of the Union Army of the Potomac's intelligence and counterintelligence operations. Both Maj. Gens. Joe Hooker and George G. Meade relied upon cavalry, the Signal Corps, and an intelligence staff known as the Bureau of Military Information that employed innovative concepts to gather, collate, and report vital information from a variety of sources.

Thomas Ryan is the former president of the Central Delaware Civil War Round Table, and a longtime member of the Gettysburg Foundation and the Civil War Trust. He has published more than 125 articles and book reviews on Civil War subjects, many dealing with intelligence operations, and writes a bi-weekly column called “Civil War Profiles” for Coastal Point, a Delaware newspaper. He is the author of Essays on Delaware during the Civil War: A Political, Military and Social Perspective (2012). Ryan served three years in the United States Army and more than three decades with the U.S. Department of Defense in various intelligence operations-related capacities. Now retired, he and his wife live in Bethany Beach, Delaware.