 In 1859 he was sent on the expedition to Harper's Ferry to suppress John Brown's raid.Tidball served all through the Civil War, receiving five brevet commissions for gallant and meritorious conduct on the field, and being complimented personally by President Abraham Lincoln for his work at the Battle of Gettysburg, where he was in command of the Second Brigade Horse Artillery under Major General Alfred Pleasonton.He served in most of the major campaigns in the Eastern Theater, from the First Battle of Bull Run through the Siege of Petersburg.