In 1858, John F. Callan, former Clerk to the Military Committee of the U. S. Senate, wrote a book, Naval Legislation of the United States. With the outbreak of the Civil War and the prospect of millions of men under arms, Callan turned his attention to the Army. Winfield Scott, as the Army’s general-in-chief, was pleased. It is likely that Callan contacted him for his opinion or for a testimonial.
Letter Signed, Washington, Head Quarters of the Army, August 7, 1861. “A republication of the military laws is very much needed at this time & the new edition by Mr. Callan containing all the laws in full & embracing those passed at the called session of this year will be very useful to the public service.”
The book that resulted, Military Laws of the United States Relating to the Army, Volunteers, Militia, and to bounty lands and pensions, from the foundation of the Government to the Year 1863, became the definitive work in the field.