The book “A System of Target Practice”, written in 1858 by Henry Heth and published in 1862 by the War Department, is cited as the US military’s first marksmanship manual. Heth graduated from West Point in 1847 and fought for the Confederacy during the Civil War.
The full text of the book from archive.org is here. A scan of the book’s pages can be found here.
The book is basically an instructor’s guide on how to teach others the skill of shooting muzzleloading rifles in combat. It includes “modern” concepts such as benchrest shooting, dry fire (using caps and blank cartridges), and use of reactive steel targets. The author claims that in 1856, using the no-live-fire training methods described in the book one unit produced a 300% improvement in shooting skill without firing a single ball.
It discusses long range shooting (at 200 yards, aim at the head, at 150 aim at the throat, 100 aim at the chest) as well as volley fire and shooting in relays.
While the book doesn’t specifically address pistols, all the concepts of marksmanship apply, from the detailed instructions on how to teach trigger press to explanation of aiming and trajectory. The book defines some very basic standards (Heth’s version of “minimum acceptable”) for soldiers, and defines a rating system where awards can be given for good scores.
Most of my research into the history of handgun shooting technique is focused on 20th and 21st century material, but this book was an interesting short read and a reminder that the basic concepts and methods of firearms instruction have been around for centuries.