Henry Thomas Harrison Henry Thomas Harrison ( 1832 – October 28 , 1923 ) , known to most simply as " Harrison " , was a spy for Confederate Lt . Gen . James Longstreet during the American Civil War . He is most well known for the information he gave Longstreet and Gen . Robert E . Lee in the Gettysburg Campaign , which as a result , convinced Lee to converge on Gettysburg , Pennsylvania , thus causing the Battle of Gettysburg . Early life and early Confederate States Army service . Harrison was born in Nashville , Tennessee . He was an actor who did not get many large parts due to his small stature . At age 29 , at the start of the Civil War in spring 1861 , Harrison joined the Mississippi State Militia as a private . Career as a Confederate spy . In November 1861 , Harrison was discharged from the Militia and eventually became a spy for CSA Secretary of War , James Seddon . In April 1863 , Harrison met James Longstreet during the Battle of Suffolk . From that point on , Harrison provided information for Longstreet , which usually proved to be reliable . Also , to maintain the loyalty of his prized spy , Longstreet frequently paid Harrison in U . S . gold coins and / or greenbacks . On the night of June 28 , 1863 , Harrison came to General Robert E . Lee with information about the Union positions . Lee had never heard of Harrison before , yet he came compliments of Longstreet , who had known Harrison since the beginning of that year . In addition , Longstreet ' s chief of staff , Moxley Sorrel , said that Harrison " always brought true information . " In the end , Harrison ' s information was plausible enough for Lee to halt his entire army . Harrison reported that the Union had left Frederick , Maryland , and was moving northward , which was true . As a result of Harrison ' s information , Lee told all of his troops to concentrate in the vicinity of Cashtown , PA , eight miles from Gettysburg , thereby triggering the events that led to the Battle of Gettysburg . Lee even said after hearing the news from Harrison , " A battle thus became , in a measure , unavoidable . " After Gettysburg , Harrison operated mostly in the North , gathering intelligence while living in New York with his newly wed wife , Laura Broders , yet none of his future intelligence ever matched the importance of his discovery in the days before the Battle of Gettysburg . Postbellum . After the war , Harrison took his wife and daughter to Mexico . But in 1866 , facing marital difficulties , Harrison left Mexico to prospect for gold in Montana . For the period of 1867 to 1892 , Harrison ' s exact whereabouts remain unknown . Laura Broders assumed that he was dead and later remarried . In 1893 , Harrison moved to Cincinnati , Ohio . In 1901 , Harrison got a job in Cincinnati as a detective for the Municipal Reform League . In 1912 , he moved to Covington , Kentucky and applied for a Confederate pension . On October 28 , 1923 , Harrison died in Covington at the age of 91 . He is buried at Highland Cemetery in Fort Mitchell , Kentucky . In Popular Culture . Harrison was a major character in Michael Shaara ' s historical novel " The Killer Angels " , and was played by Cooper Huckabee in the film version " Gettysburg " .