Pair of bound notebooks, each approx. 144pp. 8vo., belonging to Sgt. H.D. Hayes of the 101st Engineer Battalion. Notes inside the front cover of each notebook tell us that Hayes trained at the U.S. Naval Academy from 1914-1916, and at the Allied Expeditionary Force training ground at Gondrecourt in 1917, before attending the Army Engineer School in 1918. These notebooks likely date from this latter posting, as both contain copious notes on various engineering topics, including pontoon and traditional bridges, trenches, obstacles, gun emplacements, communications, supply requisitions, types of artillery fire and projectiles, and how to build defenses against them. All of these topics are accompanied by copious pencil and ink illustrations and diagrams, most notably a series of very detailed profile views of nine types of trenches. Several tactical subjects are also featured, including notes on artillery which feature insights such as: "Counter Preparation: Shell with 75's, T.M's the Boche [German] trenches & lines of communication. Big guns, counter battery work, communications, attacks on villages. To kill Boche inside of his trenches ... Barrage on Boche when they leave their trenches in 'No Man's Land'. Barrage only used when you have Boche in the open..." Hayes records his name several times in each book, and accompanying the lot is a real-photo postcard depicting Hayes in uniform. Both bear expected age wear, else very good.